Return Equipment Problem

I moved but retained my Verizon Accounts. The technician came and installed two HD set top boxes and the router. Meanwhile, at the old house I had received the box for returning the same equipment. I did that, 2 STBs, router, remotes, misc cables, more than a month ago. On my current bill, however, there is a note that I need to return 1 HD set top box or face up to a $650 charge.....what's going on, you get no receipt or anything when you mail the stuff in, but I know I did mail it in.