XM radio XM trying to scam me Internet

 I have been a customer for years. 1st of this year I started my service back up online via chat. I agreed to $25 for 6 months. Nothing else was mentioned. In the past I would pay and when it ended my service would cutoff. However this time the service was interupted like in the past but then I received a 18$ bill for 1 month. I got online and spoke to xm about this and they advised me it auto renews at regular cost. I advised I was never told this. XM basically said to bad you owe it. I told them i would pay this plus the difference to start my service back but again I was advised I had to pay the 18$. This was really upsetting me. I told them forget it and I will not renew and since its already cutoff I am finished. well to this day (A few months later) my bill has grown to 51$. I decided to call xm and they tell me its in collections. I call collections(very unprofeesional) and I tell them whats going on. Bascially XM will never get me as a cust or the money they think I owe. Its ashame a crappy company cant add up what I have paid in the past years and bank on that instead of trying to scam me