Cant get hold of cancellation dept

In January 2015 I suprised my wife with a new car, I had contacted tracker to transfer the contract from the vehicle that I was trading in to my wifes new car. As the vehicle had an old unit, I requested that if possible, a new unit be installed in my wifes new car. This was agreed and a new unit was installed in the new vehicle. I am currently still paying for the vehicle that was traded in, I have called several times to sort this out and each time I am told to speak to cancellations dept. No one in cancellations dept knows how to answer a phone, each time I hold for atleast 10min and eventually end the call due to pure frustration. I have also sent numerous emails and this doesn't help. I have even requested that they retrieve the recording of this conversation where the request was made, each time when I follow up I'm told to speak to cancellations dept. No one answers those phones, does such a dept even exist. I have for the past 2 months paid for a vehicle that I do not own and in 2 weeks I will be expected to pay again for a vehicle that I do not own. Hopefully when I eventually get to speak to someone, I will get this sorted out and get my money back.