Harassment to pay for a service I never received.

I cancelled a contract with Cartrack on the same day of installation of a unit after they gave me a package I didn't agree to. The cancelation was AT NO COST. Call recordings attest to my claim. Now their accounts department is harassing me for payment I know nothing about. Call recordings prove:

1. The reason I cancelled (I was **** to about cost of a package) 2. The date of cancelation.

But accounts department says there's nothing they can do about, I need to pay up. Customer service says only accounts can help. I'm sent from one department to another and getting calls every morning and afternoon.