Sirius XM Lied to me, then sent my bill to a collection agency New York, Nationwide

I ended my service with Sirius XM because of major customer service problems, literally every phone call would lead to 3 different transfers and someone saying "I'm sorry, I have no idea why you were transfered to me, please start over."

So when I canceled my service I called to make sure I wasn't responsible for returning any of the equipment I'd been sent a few months previous, which i was sent because their radios constantly break.  Derek, at XM Customer Service said I do not owe anything unless I wanted to continue my service, but if I was canceling I owe nothing. 

2 months later I received a notice from a collection agency.  When I called XM about this, I learned that Derek, having realized his mistake in telling me the money I owed was for service, not equipment, fraudulently documented that he had told me I still owed $31, now $36 because of the late fees. 

This is an absolute lie, and now my credit is being hurt because Derek chose to cover his a*s rather than fix his mess.  XM refused to help or contact the collection agency in any way, despite tacitly admitting this problem sounded "familiar."  They are simply the worst company I have ever dealt with.  I had originally intended to reestablish my service but now will boycott them forever.  Sirius XM deeply hates their customers.