Most painful carrier moves have the same cause: all traffic moved on one day, and problems only showed up at full volume. A staged cutover takes a little longer and gives you a way back at every step.
Run both carriers in parallel
Add the new carrier as a second trunk and keep the old one live. In VICIdial this means a second carrier entry and a dial-plan prefix you can switch per campaign. Our VICIdial and Asterisk guides show the configuration.
Before any live traffic, make test calls to your own handsets in each destination and confirm the caller ID shown, audio in both directions and that hang-ups are seen promptly on both sides.
Shift traffic in steps
| Step | Share on new carrier | Move on when |
|---|---|---|
| 1 | One campaign, low volume | CLI and audio confirmed on live calls |
| 2 | About 10% | ASR and ACD within your tolerance of the old carrier |
| 3 | About 50% | No rise in 4xx/5xx responses or agent complaints |
| 4 | 100% | A full working day at 50% with stable metrics |
Compare the two carriers on the same campaign and hours of the day, because list and time of day change ASR more than most routes do.
What to watch at each step
- ASR and ACD against the old carrier on the same traffic. Calculate them with the ASR, ACD & NER calculator.
- SIP responses: a jump in 403, 486 or 503 points to capacity, authorisation or CLI issues. See SIP response codes for dialers.
- Channels and CPS: make sure your dialer’s ratio does not exceed the trunk’s limits. Sizing channels and CPS explains the arithmetic.
- Bandwidth at your site if you also changed codec. The SIP bandwidth calculator gives the per-call figure.
Agree rollback rules before you start
Write down the thresholds that send traffic back to the old carrier, such as ASR more than a set number of points lower for an hour, or caller ID not shown on test calls. When the rule is agreed in advance, rolling back is a routine dial-plan change rather than a debate during a busy shift.