Traded iphone Anyway to get the IMEI Number?

Is there anyway to find the IMEI on a phone you traded? I sent the traded phone in the orginal box and the purchase agreement that phone does not contain the IMEI or the serial number on the contract. AT&T has given me the run around for over seven months now. When I inquire on the status half of the Reps can pull up the traded iphone's IMEI and the other half can't and I never get a response to the ticket submitted. The tracking is also all jacked up having me trading the phone before I even ordered my new phone.