Query not being resolved efficiently

I currently have a situation going on , whereby Netstar fitted 2 identical tracking devices on 1 car , so instead of me cancelling the contract I asked if they can just transfer the contract onto my new car , they demanding me to pay R650 yet this was their mistake from the start and for the past 4 months I've been billed twice for the same car which is unacceptable, they still expect me to pay for the transfer , how do you treat your loyal customer like that ? Also this has been going on for almost 2 weeks they keep saying they will get back to me everyday it's a different person and I have to start explaining my story from scratch every single time . I am so annoyed at this stage would not recommend Netstar to anyone .