SIP Trunks in Great Yarmouth

SIP trunking for businesses with an existing PBX - replace ISDN lines with cost-effective, flexible SIP channels managed by Crushed Ice. Serving businesses in Great Yarmouth and surrounding areas.

ISDNFully replaced - keep your existing on-premise PBX

40–60%Typical cost saving vs legacy ISDN lines

All DDIsPorted across with no disruption to your numbers

SIP Trunks in Great Yarmouth

SIP (Session Initiation Protocol) trunks replace traditional ISDN and PSTN telephone lines by carrying calls over your internet connection. With the Openreach ISDN switch-off now complete, any business still running an on-premise PBX needs SIP trunks to maintain PSTN connectivity. Crushed Ice supplies and manages SIP trunks with right-sized concurrent call capacity, competitive per-minute call rates, full number porting for all your existing DDIs and main numbers, and configurable failover routing. If you want to keep your existing phone system hardware but need to replace your ISDN lines, SIP trunks are the answer. Worth noting: our full hosted phone system offering includes one SIP trunk per user as standard, so there is no need to think about concurrent channel provisioning at all. For businesses considering a full system replacement rather than just ISDN migration, our hosted PBX is worth a conversation.

Crushed Ice provides sip trunks to businesses throughout Great Yarmouth — remote configuration and on-site deployment handled as standard.

Also known as:SIP TrunkingSIP LinesISDN ReplacementISDN AlternativeIP TrunksVoIP TrunksSIP Provider

What's covered

PBX Compatibility

SIP trunks work with virtually all on-premise PBX systems: Avaya, Mitel, Panasonic, Cisco, Asterisk, 3CX. We test compatibility before provisioning.

Number Porting

Port your existing geographic numbers, DDIs, 0800, 0845, and 03 numbers to SIP. No changes to your public-facing numbers.

Elastic Channels

Concurrent call channels scaled to match your actual usage. Add capacity in hours, not weeks. No over-provisioning required.

HD Voice Quality

G.722 wideband audio delivers noticeably clearer call quality than traditional ISDN, provided you have a suitable internet connection.

Lower Call Costs

Competitive UK, European, and international per-minute rates. Most businesses save 20–40% on their call costs compared to ISDN equivalents.

Failover Routing

We can configure incoming call diversion so that if your internet connection fails, calls are redirected to mobile numbers or a backup destination rather than simply ringing out. This is available as a configurable option on all SIP trunk deployments.

How it works in practice

Emergency ISDN Replacement

The situation

A legal firm's telecoms provider gave 30 days notice that their ISDN30 circuit was being withdrawn. They had an on-premise Panasonic PBX they were not ready to replace.

The result

Crushed Ice provisioned SIP trunks compatible with their Panasonic system within a week, ported their 25 DDIs, and cancelled their ISDN contract, saving £340 per month in line rental.

Multi-Site Single Bill

The situation

A property company had three offices each with separate ISDN lines, separate telecoms providers, and three separate monthly invoices. Call transfers between sites went via the PSTN, incurring per-minute charges.

The result

SIP trunks from a single provider, centrally managed by Crushed Ice, replaced all three sites' ISDN lines. Internal site-to-site calls became free, and three bills became one. A 35% overall cost reduction.

Burst Capacity for Seasonal Demand

The situation

A retail business with a customer services team needed additional call capacity during peak periods (November–January) but was paying for excess ISDN channels year-round.

The result

SIP trunks with elastic capacity allowed them to scale from 10 to 25 concurrent channels for peak season and back to 10 in January, paying only for what they actually used.

Significant Cost Reduction Without Changing the PBX

The situation

A distribution company was happy with their existing Mitel PBX but their ISDN bills had become excessive, over £800 per month for line rental and calls.

The result

Crushed Ice replaced their ISDN lines with SIP trunks, keeping the Mitel system unchanged. Monthly telecom spend dropped from £820 to £380, a 54% reduction, with improved call quality.

Porting your numbers

Capacity Planning

We analyse your current call volumes and concurrent call patterns to determine how many SIP channels you actually need. Most businesses are over-provisioned on ISDN. SIP lets you right-size immediately.

PBX Configuration

We configure the SIP trunk registration on your existing PBX: codec settings, registration credentials, dialplan adjustments, and failover rules. This is done remotely and typically takes two to four hours.

Number Porting

We initiate porting of your existing numbers from your current ISDN provider. Numbers are ported with your PBX handling both old ISDN and new SIP trunks in parallel during the transition, with no downtime.

Testing & Go Live

We perform end-to-end call testing: inbound, outbound, DDI routing, voicemail, and failover, before confirming go live. Ongoing management is included in your monthly agreement.

Delivered as part of our Business VoIP Phone Systems service

SIP Trunks is a core part of how Crushed Ice delivers Business VoIP Phone Systems. All of our services run on a simple all-inclusive monthly fee — no large upfront costs, no hidden extras, and direct access to the people who actually look after your systems.

View Business VoIP Phone Systems Get a free quote

SIP trunks - common questions

Providing SIP Trunks to businesses across NR30, NR31, NR29 in Great Yarmouth

What's covered

PBX Compatibility

SIP trunks work with virtually all on-premise PBX systems: Avaya, Mitel, Panasonic, Cisco, Asterisk, 3CX. We test compatibility before provisioning.

Number Porting

Port your existing geographic numbers, DDIs, 0800, 0845, and 03 numbers to SIP. No changes to your public-facing numbers.

Elastic Channels

Concurrent call channels scaled to match your actual usage. Add capacity in hours, not weeks. No over-provisioning required.

HD Voice Quality

G.722 wideband audio delivers noticeably clearer call quality than traditional ISDN, provided you have a suitable internet connection.

Lower Call Costs

Competitive UK, European, and international per-minute rates. Most businesses save 20–40% on their call costs compared to ISDN equivalents.

Failover Routing

How it works in practice

Emergency ISDN Replacement

The situation

A legal firm's telecoms provider gave 30 days notice that their ISDN30 circuit was being withdrawn. They had an on-premise Panasonic PBX they were not ready to replace.

The result

Crushed Ice provisioned SIP trunks compatible with their Panasonic system within a week, ported their 25 DDIs, and cancelled their ISDN contract, saving £340 per month in line rental.

Multi-Site Single Bill

The situation

The result

Burst Capacity for Seasonal Demand

The situation

A retail business with a customer services team needed additional call capacity during peak periods (November–January) but was paying for excess ISDN channels year-round.

The result

SIP trunks with elastic capacity allowed them to scale from 10 to 25 concurrent channels for peak season and back to 10 in January, paying only for what they actually used.

Significant Cost Reduction Without Changing the PBX

The situation

A distribution company was happy with their existing Mitel PBX but their ISDN bills had become excessive, over £800 per month for line rental and calls.

The result

Crushed Ice replaced their ISDN lines with SIP trunks, keeping the Mitel system unchanged. Monthly telecom spend dropped from £820 to £380, a 54% reduction, with improved call quality.

Porting your numbers

Capacity Planning

PBX Configuration

Number Porting

Testing & Go Live

We perform end-to-end call testing: inbound, outbound, DDI routing, voicemail, and failover, before confirming go live. Ongoing management is included in your monthly agreement.

Delivered as part of our Business VoIP Phone Systems service