Definitely a no-go over the phone. Like with most SDC rule-bending, you're much more likely to be successful at the airport than over the phone.

One caveat:
I've heard that priceline tickets are very hard to reissue in the delta systems. Given that, you're much more likely to be successful if your desired flights have the exact same routing as your original flights.

I tend to not mind risking things like this, but given that you'd be changing to a later flight, I probably wouldn't do it.