CUCM - Transfer External then Release Call

[jf05]

We currently have an extension set up to Forward All calls to an external number. This is working perfectly however what we are learning is that CUCM is hanging onto the call after the transfer occurs as we are getting the total call time charged through AT&T. Is there a way to transfer the call and have CUCM be done with the call and release it? Not sure if this type of transfer exists.  For some reason, just very recently we are getting call charges for hours upon hours after they are transferred to this external number (which is our external cloud call center). If they press 0 to talk to an agent, and CUCM transfers the call externally to the cloud call center, I would like CUCM to terminate the call on our end so it has nothing to do with the call anymore. Is this possible?

[Jaime Valencia]

That depends a lot on what you use for PSTN and then if your telco supports something like TBCT

https://community.cisco.com/t5/ip-telephony-and-phones/setup-of-2-b-channel-transfer-tbct-on-cisco-voice-gateway/td-p/2034849

So, I'd start by asking your telco, as TBCT was only supported by very few telcos when ISDN was the most common option for PSTN