Not sure why you would want to do that any way
I usually turn off drt to prime . I had a customer who had me back several time because they thought one of their trunks was dropping calls.
The guy in the shop would put a call on hold or transfer to another department and forget it. It would eventually transfer to the receptionist, but by then the caller had hung up and when the receptionist would answer what she thought was a new incoming call. She would just get dead air, and blame the phone co (me) for an incoming line that was always cutting off her customers. Totally convinced that she was losing thousands of dollars.
I think that was before DS, but I still think that call backs should go to where they came from. otherwise customers end up being transferred all over the place because no-one knows where they have been or how many times they have been transferred.
I know the customer is always right but sometimes they need a little push in the right direction.