If I understand correctly, you want to take an incoming call, have your operator answer it, then transfer it to an outside number.
This can be done.
First be sure your operator can call the outside number.
Next check the COS of your trunks and the COS of your operator and be sure they both enable "public network to public network" connections.
That should be all.
But...
It is possible that depending on your trunk types, you may have issues with the source caller ID. In essence, it is possible that when your operator transfers the call outbound that the caller ID presented is the that of the inbound caller. Your carrier may view that as an invalid call. If you've double checked your COS and you still have an issue then let us know. We'll try and walk you through a change.
Ralph