Migrating an Enterprise Phone System: PBX to VoIP
Migrating an Enterprise Phone System: PBX to VoIP
25+ offices and a call center were running on a legacy Verizon PBX system, with 5,000+ numbers that needed to move to cloud VoIP over SIP without disrupting service. The call center couldn't go dark, even for a minute, and neither could the fax lines. Underneath the number-porting problem sat a second one: the IVR call-routing logic, including the auto attendant, was complex, undocumented in many places, and had to be rebuilt and tested before a single office cut over.
Five things had to go right at once, across 25+ offices that don't run on the same clock.
- Porting 5,000+ phone and fax numbers with zero downtime on critical lines
- Migrating and re-validating complex IVR call-routing logic
- Managing overlapping Verizon/Vonage billing to avoid double charges
- Coordinating site readiness and legacy equipment disposal across 25+ offices
- Training staff on new phones and voicemail access before cutover
Ran a phased, office-by-office migration with live-tested IVR redesign and a shared billing dashboard to catch overlap charges before they happened.
The number that mattered most here was never on the invoice: zero. Zero dropped calls the day of cutover, across every office. That's what phased planning and a shared tracking dashboard buy you: not a faster migration, a boring one.