Question on Returned Equipment

Canceled Uverse and returned the four receivers, remotes, etc to AT&T via UPS a week ago. Received email from AT&T the next day showing three receivers were received. Want to check to see if four were received.........have a receipt showing four receivers with serial numbers were given to UPS for return.

Please advise how I find out if all receivers were received by AT&T.  Want to get it settled before it's an issue.