Bad treatment by netstar tracker

I had a 36 months contract with Netstar tracker and after that their tracking device went out of warranty and was no longer functioning well, I reported this that the device is not working asking for them to replace it and provide me with remotes. No one came back to me as promised now they are saying I'm owing them and I don't have contract with them.

They have send my details to credit collection companies without even trying ask me why or maybe asking for payment

I want them to remove my name on credit collection companies