I was just thinking about how the agent could generate ephemeral PBX extensions. OTP-like would definitely be the way to go.

Edit: perhaps the extension would be per transaction, not per-agent, and when the customer calls the extension, the agents system can automatically pull up the customer’s account. These extensions should expire, but given the length of some customer calls, and how often I’ve been disconnected from customer service lately, perhaps it should be on the order of hours, not minutes or seconds