PSTN call transfers not working

Question

Hello Teams Community,

Please I need your help on this.

we are having issues transferring incoming PSTN calls that come in through an Auto-attendant and Call queue and are answered by an employee and being transferred to an external PSTN number with the consultive transfer.

Also for more clarification I am not talking about an auto attendant transferring calls?

What I meant is that when a User is answering a call that came in through an auto attendant & Call queue. So this happens when a Teams client User (normal user with licenses) does a consultive transfer to a PSTN number.

The User that answered the call on their Teams client gets an error that the transfer is not working, and they get 2 call screens on hold with both the caller, and the person where the transfer would need to go to.

We can use 2 options when transferring calls. Cold transfer (without consultation) and with consultation (warm transfer). When using the cold transfer option to transfer the caller to the external PSTN number, there is no problem.

They are not having this problem when transferring with internal users. We also own the SBC infrastructure, and we cannot see any error there.

Transfers without consulting, cold transfers, are working. You could see this behaviour at the call with the ID: 8ec345aa-7818-46a3-8172-8d875cf59eff