Originally Posted by
NY-FLA
The presumption that it's paid for is what's creating your disconnect. I think you might need some good status with the other airline (as I do with UA) to get them to give a res. on the promise of a write-over. The other option is to buy the ticket on the other airline that has the 24 hour canx after booking policy, if not flown, and work with them to swap your bought booking with the interline. (WARNING! NB: this will not work on USAir)
If other airlines still allow a reservation to be made without actual ticket purchase, then that's another thing. I do not know which carriers actually allow reservations without a ticket purchase.
However, even if you buy a ticket with a 24 hour cancel policy (which carriers beside DL allow that?), then attached to that ticket is a ticket number, form of payment etc. It is usually difficult to change even the form of payment.