Has anyone worked implementing a vapi agent for clients that already have their established phone lines? What's the process? Does the phone number have to be ported to twillio/vonage so it can be used? Or has anyone done anything else like redirecting all incoming calls in the client's existing system to the agent's free phone number provided?

Watching

Yes, you can port the number, but technically that means they don't really own it anymore, or the provider they were using, as it's now a number owned by Twilio (or whoever you port it to). It works, but it takes verification and it's a process (wait time like 1-2 weeks). Call forwarding is usually the route of action, or conditional call forwarding with their phone set to do not disturb so that calls on their contact list ring through while unidentified callers get transferred to the agent.

Damn that's really smart. Didn't know that was possible. My client is a small/local bank branch. They want to replace the automated system ("Welcome, press 1 for this, 2 for that...") to route calls and answer basic questions. If I just forward all the calls, would the agent see the calls coming from their existing phone number, or actually from the client's number?

from the clients (the actual caller's number).