I recently had a $75 mail in rebate, but could not use it because it was canceled. They are doing the 22 month upgrade now. I called customer service yesterday and the woman i talked to asked if i wanted to credit it to my monthly bill, So i did that. I get to skip a monthly bill and sprint pays for it. I advise you to call sprint and do the same.
I got the same offer but it was with the stipulation that I renew my contract for 2 yrs. You might want to call and check and see if that's what happened to you. When I found that out I politely told the rep I did not want to renew for a measly 80$ then be back in the same boat next year when another device I want is released.
I would report this to the Federal Trade Commission and I promise you will get proper action from Sprint Executive team. I have had to resport to that line of resolution for issues that could have been handled at a lower level of resolution. It is pthetic that we would ned to do that but do. report them. They nickle and dime us to death and that is the way it is.