I called XM last month, because my year was coming up for renewal, and I basically told them from the start, that either I would be cancelling my service, or they would renew me for the $77/year. Having Satellite Radio isn't worth the $13/mo or so to me, but half that price most definitely is worth the price. They came back originally and told me that the special was no longer available, and would I like to get 3 months free service instead. I said nope, cancel my account. They kept trying other 'tempting' offers, but none matched the $77/year. I finally told them one more time, that I don't have time to sit here and tell them what I want and they either need to renew me at the $77/year price, or cancel my service now. They put me on hold for a few minutes and came back and told me that they had approval to do so.
So that's what you need to do, call in to cancel the account, and be VERY insistant on them honoring that price -- OR -- you could go about it a different way, and say you received a postcard in the mail stating that you were elgible for the $77/year special.. What are they going to say?
good luck!