--- title: SIP Trunks in Stevenage - Crushed Ice Ltd description: SIP trunking for businesses with an existing PBX - replace ISDN lines with cost-effective, flexible SIP channels managed by Crushed Ice. Serving businesses in Stevenage and surrounding areas. url: https://crushedice.uk/services/sip-trunks/hertfordshire/stevenage --- # SIP Trunks in Stevenage - Crushed Ice Ltd > SIP trunking for businesses with an existing PBX - replace ISDN lines with cost-effective, flexible SIP channels managed by Crushed Ice. Serving businesses in Stevenage and surrounding areas. --- ## About SIP Trunks 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. **Also known as:** SIP Trunking, SIP Lines, ISDN Replacement, ISDN Alternative, IP Trunks, VoIP Trunks, SIP Provider ## SIP Trunks in Stevenage Crushed Ice provides sip trunks to businesses throughout Stevenage. Whether you're based in the town centre or surrounding areas, our team delivers the same level of service - remotely or on-site as needed. **Areas covered:** Town Centre, Old Town, Pin Green, Broadwater, Shephall, Bedwell, Gunnels Wood, Stevenage Business Park, Martins Wood, St Nicholas ## What's included ### 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 **1. 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. **2. 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. **3. 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. **4. 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. ## Real-world scenarios ### Emergency ISDN Replacement **Scenario:** 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. **Outcome:** 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 **Scenario:** 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. **Outcome:** 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 **Scenario:** 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. **Outcome:** 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 **Scenario:** 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. **Outcome:** 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. ## Frequently asked questions ### Does SIP trunking work with my existing PBX? In the vast majority of cases, yes. SIP trunks are compatible with virtually all modern on-premise PBX systems: Avaya, Mitel, Panasonic, Cisco, Asterisk, 3CX, and many others. We test compatibility before provisioning and configure the trunk registration on your existing system. Very old hardware may require an analogue terminal adapter, which we can also supply. ### ISDN has been switched off - what do we do now? SIP trunks are the direct replacement for ISDN. If your existing PBX has SIP capability (most do), we configure SIP trunks and port your numbers across. Your PBX continues to operate exactly as before. You simply no longer have a physical ISDN connection. The process is straightforward and typically takes under two weeks from order to go live. ### How many SIP channels do we need? The number of concurrent channels equals the number of simultaneous calls your business needs to handle at peak - both inbound and outbound combined. Most SMEs need between 4 and 20 channels. We can analyse your call records to calculate the right number, and elastic SIP lets you add channels in hours if you underestimate. ### What happens to our numbers when we switch? Number porting transfers your existing geographic numbers, DDIs, and non-geographic numbers to your new SIP provider. The process typically takes 5–10 working days, during which both old and new systems run in parallel. Your public-facing numbers do not change. --- **Phone:** +44 (0)1234 672 612 **Email:** hello@crushedice.uk **Service page:** [SIP Trunks in Stevenage](https://crushedice.uk/services/sip-trunks/hertfordshire/stevenage) --- *Crushed Ice Ltd - Unit 11, Olney Business Park, Osier Way, Olney, Buckinghamshire, MK46 5FP*