A couple years ago my dad moved, and cancelled his cable service with Comcast. They told him he needed to drop off his cable box at some return center, to which he told them "If you want it, you can come pick it up, but I won't go out of my way to drop it off..."
When he moved, he took the box with him, and after two years he finally threw it away. Ironically, a week after he tossed it, he got a collection letter saying Comcast wanted $150 for non-returned equipment.
There are already broad/generic validation letters on this board, but I like to make more specific letters.