Migrating from Twilio's Elastic SIP Trunking service to Programmable Voice requires preparation, testing, and migration of the SIP trunk and Twilio numbers. The process involves implementing Twilio Functions to control inbound and outbound calls, creating a new SIP Domain for PBX calls, and configuring Programmable Voice for both Inbound and Outbound calls. Optional configuration options include securing media, using localized SIP URIs, and adding custom parameters to SIP calls. Bulk migration of numbers can be achieved by using the Twilio API to programmatically configure the numbers. The move to Programmable Voice provides full control over incoming calls, enabling features like IVRs, AI chatbots, near real-time voice transcription, Agent Assisted Payments, and more.