SIP Trunks that scale with your call volume
Replace legacy phone lines with flexible SIP channels delivered over your IP connection. Keep your current phone system, contact centre or UC platform, and increase (or reduce) concurrent calls as your needs change.
Tested interoperability with leading phone systems and gateways.
What is SIP Trunking?
TalkAssure™ SIP trunking gives you virtual telephone lines (channels) delivered over a high-speed IP connection, so your call capacity is no longer constrained by physical circuits.
Add the call capacity you need for simultaneous calls, then adjust it as your organisation grows or changes, without installing extra phone-line hardware.
Estimate your SIP trunk requirements
Use a simple rule-of-thumb calculator based on typical industry ratios to see how many concurrent call channels you may need. Adjust the sliders to match how your teams actually work.
How call-heavy is your environment?
Spare capacity for peaks / resilience
SUGGESTED STARTING POINT
18 concurrent call channels
Based on 50 users in an Office / mixed roles environment, including approximately 20% spare capacity for peaks and failover.
Typical office environments often start around 3–4 users per channel. Call-heavy teams and contact centres work better with lower ratios (more channels per user).
- Enough capacity for your busiest hour without constant busy tones.
- Headroom to handle marketing campaigns, seasonal peaks or site outages.
SIP Trunk Small Office
Ideal for small offices, branch sites or first-time SIP deployments.
from £29.95 / month
- 5 simultaneous inbound or outbound calls
- Includes call plan
- UK & international numbering options
- Free porting of existing numbers
- Fraud detection, prevention and call barring included
Business SIP
For growing teams and busy single-site deployments
from £49.95 / month
- 10 simultaneous calls
- Includes call plan
- UK & international numbering options
- Free porting of existing numbers
- Works with Microsoft Teams
- Compatible with most VoIP phone systems
Call Centre SIP
For contact centres or multi-site organisations
from £99 / month
- Start with 30 simultaneous calls and expand
- UK & international numbering options
- Advanced fraud detection and call barring controls
- Suitable for resilient, multi-site and data centre designs
Final pricing will depend on the number of channels you take, the call plans you pair with your trunks and any international numbering requirements. Use this as a guide, then request a quote for a tailored proposal.
Big Savings
Small upfront investment and significantly lower call rates than traditional fixed lines.
Flexibility
Add or remove SIP channels as required, without ordering new physical lines or hardware.
Unified voice & data
Run voice and data over a converged connection and dynamically allocate bandwidth based on demand
Business Continuity
Automatic call re-routing keeps you reachable even if your main site, PBX or connectivity has issues.
Interoperability
Tested with leading IP PBXs, SBCs and gateways including 3CX, Asterisk, Avaya, Cisco, Mitel, Yealink and more.
Microsoft Teams Ready
Use SIP trunks with Telappliant Voice for Teams to make and receive calls directly in your Teams client.
Yes. TLS and SRTP can be supported, with SBCs and network controls to protect voice traffic.
Yes. Number porting and hybrid setups are possible during migration.
Support is available for major IP PBXs, contact centre platforms and cloud UC providers.
Yes. For further security we can support TLS and SRTP, with SBCs and network controls to protect voice traffic.
Yes. We support number porting and hybrid setups during migration.
We support all major IP PBXs, contact centre platforms and cloud UC providers.
Why SIP trunks replace legacy lines so well
Lower cost than legacy lines
Reduce reliance on line rental and move voice onto IP with competitive call rates and minimal upfront change.
Scale channels when demand changes
Increase or reduce concurrent call capacity without installing additional physical lines.
Converged voice + data
Run voice and data over one connection and allocate bandwidth where it’s needed.
Continuity & rerouting
Automatic call re-routing helps keep customers and teams connected if something goes wrong.
How SIP Trunking works
Replace fixed phone lines with flexible call capacity
SIP trunking replaces traditional phone lines with cloud-based call capacity delivered over your data connection.
Instead of being limited by physical circuits, your existing phone system can support more (or fewer) simultaneous calls as your needs change, without additional line installs.
In practice:
- Choose how many channels you need now
- Add numbers and routing rules that match your setup
- Increase capacity as call volumes grow or sites change
Technical overview (for IT teams)
SIP trunking connects an IP-based phone system (IP PBX or UC platform) to the public telephone network using SIP signalling, with media carried over IP using standard compression methods (codecs). Capacity is provided as virtual channels rather than physical lines.
Using Microsoft Teams for calling?
SIP trunks can provide the PSTN connectivity needed to make and receive external calls in Teams via Direct Routing.
Want to get started?
Get a quote and a clear migration plan
Tell us what you have today (phone system/Teams, numbers, and expected call volumes). We’ll recommend channel capacity and routing options and confirm any lead times for onboarding and number changes.
Sales (new enquiries)
Book a video call (Sales)Enquiry & Support
Use the contact form for IT support enquiries, plan questions, or audit requests.