I had something very similar. I purchased my Droid X on the 15th and returned it on the 19th. However, my transaction wasn't as smooth as yours. When I returned the X not only did the rep argue with me saying how Blur can be removed (the horrible blur overlay that took over the messaging/dialpad/contacts and ruined the overall phone was the reason I returned it) they put my Droid back on the account, but they treated it as a 30 day exchange and didn't change my account back. I had no idea until about two days later when I got a call asking how I'm liking my new Droid.
So after explaining my problem, they said that they'd reverse it and I'd see everything fixed by the end of the week. Well come Friday, it wasn't fixed so I call up customer service and they were like "Oh, I don't know why they'd tell you that, we can't reverse a contract you have to go to a store" (which I know is a lie since I worked for VZW for 3 years). But it was 11PM at night so I didn't want to bother arguing. Next day my wife goes to the store because I had to work to get it resolved, and they told her they couldn't do anything and that she'd have to call customer service. So she made them do it and they told her they couldn't do it and then she asked for a supervisor and the supervisor fed her some lies and basically insisted she didn't know anything about phones and hung up on her.
So I ended up having to call up customer service, and lo and behold the person I get was able to reverse my contract (which was originally up on 11/22/10) and reversed the upgrade. The positive about that whole situation was that they put my as eligible for NE2 which I wasn't eligible until July of next year.
tl;dr
My contract end date was reversed like it should've been, and my upgrade was as well except they gave me NE2 when I shouldn't have.
