I have been paying premium for the wrong vehicle

In December I bought a car from Brynaston VW and I took over the tracker account. In January I found out that the wrong vehicle was linked to my name (DC31TWGP instead of DC25WPGP). I queried this with Tracker and was promised that it has been resolved. Last night when I could not find my vehicle I logged into my tacker only to find out that is not the case. Now this is a risk as it means that my vehicle could be lost and I wont be able to track it because even though I queried a number of times the wrong vehicle is linked to my name. I want to cancel my membership and get my refund as I have clearly been paying for the wrong vehicle.