Let it go for a month or just tell them you have decided to let it go to switch over to Sirius and they will be offering you a better deal. Try to get them down to another year at $7.00/month prepaid. It worked for a friend of mine. Otherwise, you could always get the new HD radio and have more stations in digital for free. AM in FM quality and FM in CD quality with multiple channels on each frequency.
Still I have had XM for 3 1/2 years.