However, given the fact you moved: im going to assume you forgot to cancel your service.
That is your responsibility they can charge you day after day as long as you fail to tell them.

Call, and ask to speak with a higher rep who would have access to the reason why. They're collection company should even have the information as to why you owe them.

Before implying it's the company screwing you over: Make sure you didn't screw yourself over.