Business VoIP Phone Systems | 3CX Partner UK
CSLN Group delivers enterprise-grade business VoIP phone systems to organisations across the UK. As an authorised 3CX partner, we design, deploy, and support cloud-hosted and on-premise VoIP solutions that reduce costs, improve call quality, and give your team the flexibility to communicate from anywhere.
Whether you're replacing an outdated PBX, moving to a cloud phone system for the first time, or scaling communications across multiple sites, our telecoms specialists deliver a seamless transition with minimal disruption to your business.
Why Choose CSLN Group for Business VoIP?
We're not just another VoIP reseller. CSLN Group combines managed IT support expertise with specialist telecoms knowledge, giving you a single provider for your entire technology stack. Our partnership with Spitfire Network Services — one of the UK's leading independent network providers — means we deliver VoIP over business-grade connectivity, not consumer broadband.
- Authorised 3CX Partner — certified to design, deploy, and support 3CX systems
- Spitfire Network Services Partner — VoIP delivered over dedicated, quality-assured connectivity
- Single Provider — IT support, cybersecurity, connectivity, and telecoms from one team
- UK-Wide Support — remote and on-site support from our offices in Kings Lynn, Cambridge, and Norwich
- Extended Hours — support available 6am–10pm, seven days a week
Our Business VoIP Phone Systems
3CX Cloud-Hosted Phone Systems
3CX is a software-based PBX that replaces traditional phone systems with a flexible, feature-rich platform. With 3CX cloud hosting, there's no on-site hardware to maintain — your entire phone system runs securely in the cloud, managed and monitored by CSLN Group.
- Unlimited extensions and call queues
- Integrated video conferencing and live chat
- Mobile and desktop apps for remote and hybrid working
- CRM integration (Salesforce, HubSpot, Microsoft 365, and more)
- Call recording, reporting, and analytics
- Auto-attendant and IVR menus
- Voicemail to email transcription
On-Premise 3CX Deployment
For organisations that require full control over their telephony infrastructure, we deploy and manage on-premise 3CX systems. This is ideal for businesses with strict data sovereignty requirements, large call volumes, or existing server infrastructure.
- Installed on your own hardware or virtual machine
- Full control over call data and recordings
- Lower per-user costs at scale
- Managed and maintained remotely by CSLN Group
SIP Trunking
We provide SIP trunks over Spitfire Network Services' dedicated infrastructure, ensuring crystal-clear call quality and rock-solid reliability. Unlike consumer-grade VoIP, our SIP trunks are delivered over business-grade connectivity with guaranteed bandwidth and quality of service (QoS).
- Competitive per-channel pricing
- Number porting from any UK provider
- Geographic, non-geographic, and international numbers
- Failover and disaster recovery options
- Fraud protection and call barring
Number Porting & Migration
Switching to VoIP doesn't mean losing your existing phone numbers. We manage the entire number porting process, transferring your numbers from your current provider with zero downtime. Our team handles all coordination with carriers so you don't have to.
Unified Communications
Modern businesses need more than just voice calls. With 3CX, your team gets a complete unified communications platform — voice, video, live chat, SMS, and messaging in a single interface. Reduce app fatigue, streamline collaboration, and give customers more ways to reach you.
- Voice, video, and conference calling
- Website live chat with visitor tracking
- WhatsApp and Facebook Messenger integration
- SMS and business text messaging
- Presence and status indicators across teams
- Microsoft Teams integration
VoIP Solutions by Business Size
Small Businesses (1–20 Users)
Affordable, professional phone systems that scale as you grow. Replace expensive ISDN lines with a cloud-hosted 3CX system, get a professional auto-attendant, and let your team take calls on their mobiles or laptops — no desk phones required.
Mid-Sized Businesses (20–100 Users)
Multi-site connectivity, advanced call routing, departmental queues, and CRM integration. We design systems that handle complex call flows while keeping management simple through the 3CX web console.
Enterprise & Multi-Site (100+ Users)
High-availability deployments with failover, dedicated SIP trunks, contact centre features, and integration with your existing IT infrastructure. CSLN Group manages the entire platform so your internal team can focus on strategic priorities.
VoIP for Key Sectors
Education
Cost-effective phone systems for schools, colleges, and multi-academy trusts. Features include reception console, classroom intercoms, emergency broadcast, and integration with school management systems. All our engineers are DBS-checked for safe working in education environments.
Professional Services
Law firms, accountancy practices, and consultancies benefit from call recording for compliance, CRM integration, and mobile apps that let fee-earners stay connected while working remotely or visiting clients.
Construction & Trades
Keep site teams and office staff connected with mobile-first VoIP. Calls route seamlessly between office desk phones and mobile apps, so you never miss a client call — even when your team is on site.
Healthcare
Secure, GDPR-compliant phone systems with call recording, queue management for patient enquiries, and integration with practice management software.
Why 3CX?
3CX is trusted by over 600,000 businesses worldwide and consistently rated as a leader in business communications. As an authorised 3CX partner, CSLN Group has the expertise to get the most from the platform.
- ✔ Open-standard — works with hundreds of SIP phones and gateways
- ✔ No per-user licensing fees on many editions
- ✔ Built-in video conferencing (no Zoom or Teams licence needed)
- ✔ Web, desktop, and mobile clients included
- ✔ Regular updates and security patches
- ✔ Easy management through a web-based admin console
Why Spitfire Network Services?
VoIP is only as good as the connection it runs on. That's why we partner with Spitfire Network Services, one of the UK's most respected independent network providers. Spitfire's business-grade connectivity ensures your calls are clear, reliable, and prioritised — even during peak internet usage.
- ✔ Dedicated internet circuits with guaranteed bandwidth
- ✔ Quality of Service (QoS) for voice traffic prioritisation
- ✔ Ethernet, FTTP, EFM, and broadband options
- ✔ 24/7 UK-based network operations centre
- ✔ Proactive monitoring and fault management
What's Included with Every VoIP Deployment
- ✔ Free site survey and network assessment
- ✔ System design tailored to your business requirements
- ✔ Professional installation and configuration
- ✔ Number porting from your existing provider
- ✔ Staff training and user guides
- ✔ Ongoing support 6am–10pm, seven days a week
- ✔ Proactive monitoring and system updates
- ✔ Dedicated account manager
Frequently Asked Questions
What is VoIP and how does it work?
VoIP (Voice over Internet Protocol) transmits phone calls over your internet connection instead of traditional phone lines. It converts your voice into digital data packets, delivering calls with high quality and low cost. All you need is a stable internet connection and a VoIP-compatible device — a desk phone, computer, or mobile.
Will I need new phones?
Not necessarily. 3CX works with a wide range of SIP-compatible handsets, and your team can also use the 3CX app on their existing computers and smartphones. If you do need new hardware, we supply and configure IP phones from leading manufacturers including Yealink, Fanvil, and Snom.
Can I keep my existing phone numbers?
Yes. We handle the entire number porting process, transferring your existing numbers from your current provider. There's no downtime — we coordinate the switch so calls continue uninterrupted.
Is VoIP reliable?
When delivered over business-grade connectivity — as we do through our Spitfire Network Services partnership — VoIP is extremely reliable. We implement Quality of Service (QoS) settings to prioritise voice traffic, and our systems include failover options to keep you connected even if your primary internet circuit goes down.
How much does a business VoIP system cost?
Costs depend on the number of users, features required, and whether you choose cloud-hosted or on-premise deployment. 3CX offers competitive licensing with no per-user fees on many editions. Contact us for a free, no-obligation quote tailored to your business.
Can VoIP work with remote and hybrid teams?
Absolutely. 3CX's mobile and desktop apps let your team make and receive calls on their business number from anywhere with an internet connection. Calls, video meetings, and messages all work seamlessly whether staff are in the office, at home, or on the move.
How long does it take to set up?
A typical deployment takes one to two weeks from initial consultation to go-live, depending on complexity. Number porting can take up to 10 working days depending on your current provider. We manage the entire process and keep you informed at every stage.
What happens if my internet goes down?
We configure failover options so calls can be redirected to mobile phones or an alternative circuit if your primary connection fails. With Spitfire's proactive network monitoring, faults are often detected and resolved before they impact your service.
Do you support Microsoft Teams integration?
Yes. 3CX integrates with Microsoft Teams, allowing you to make and receive external calls directly within the Teams interface. This is ideal for businesses already using Microsoft 365 who want to add full telephony without replacing their collaboration platform.
Can I use VoIP for a contact centre?
Yes. 3CX includes built-in contact centre features such as call queues, skills-based routing, real-time dashboards, wallboards, and agent performance reporting — all included without expensive add-ons.
Book a Free VoIP Consultation
Not sure where to start? Book a free VoIP consultation with our telecoms specialists. We'll assess your current setup, understand your requirements, and recommend the right solution — with no obligation and no jargon.
Ready to Upgrade Your Business Phone System?
Speak to our VoIP specialists today. Call us on 0330 363 9976, email hello@cslngroup.com, or use the contact form below to request a free, no-obligation quote.
Explore More from CSLN Group
- Business Connectivity Solutions
- Managed IT Support
- Cyber Security Services
- Education IT Support
- UK IT Support
- Business IT Support – East Anglia
Contact CSLN Group
Get in touch to discuss your business VoIP requirements. Our team is available 6am–10pm, seven days a week.
- Phone: 0330 363 9976
- Email: hello@cslngroup.com
- Offices: Kings Lynn, Cambridge, Norwich
Client Reviews: Trusted IT Support for Businesses & Schools
Over the past three years, CSLN Group has been a key strategic partner in shaping and delivering our IT strategy. Their guidance and technical expertise have supported major projects including cloud transitions, infrastructure upgrades, and improved cybersecurity.
Their collaborative approach and deep understanding of our needs have enabled us to build a more resilient and future-ready IT environment. CSLN’s support has allowed our internal team to focus on service development with confidence in the stability and performance of our core systems.
We highly value our partnership with CSLN Group and would recommend them without hesitation.
Contact CSLN — Your Business VoIP Partner
Ready to upgrade your business phone system or need expert advice on VoIP solutions? Let's talk.
📞 Call: 0330 363 9976
📧 Email: hello@cslngroup.com
🏢 Offices: Kings Lynn, Cambridge, Norwich
Or send us a message via our contact form, and we'll respond promptly to your enquiry.