Removal of tracking device

In January 2014 I wrote a note to let Mixtelematix to remove the tracking device as I got a new insurance that would like to put theirs.I called to confirm the receipt of the fax and they said they got it but I should email and I did that.From then every time I call to find out what's happening no one knew what's going on.I spoke to too many people I even lost count.They later send me an email saying I have to pay the remaining amount as I have a 3 year contract with them.My initial 2 year contract was over when they instruct me to go put a new device as the old one is outdated.I did that and paid nothing as it was not my decision to put a new device.Now they refuse to remove the device and they don't want to bring the voice recording that says I took a 3 year contract again and they promised to do that.They now handed me to debt collectors while I'm waiting for the recordings.Please help me I want this device to be removed as I'm loosing out on the benefits of the new insurance and please help clear my name at the debt collectors.I would also like them to bring the recordings that confirms my agreeing to the contract.