Transfering numbers between phones

[NokiaNovice]

I have two AT&T cellphones with expired contracts. I would like to drop the service on the first phone, but transfer that number to the second phone (thereby dropping the second phone's number). I do, however, want to keep the contract terms (mins & price) of the 2nd phone. This is what I have in detail, both AT&T issued Nokia TDMA phones.

First Phone:
Nokia 5165, easy number, old $19.99/mo plan (60 anytime, 250 n/w)

Second Phone:
Nokia 6360, hard number, old $29.99/mo plan (350 anytime, unlimited n/w)

So the end result is the first phone/plan goes away, and the second phone/plan stays with the easy # of the first phone. How do I go about doing this if it can be done at all?