Mis sold car service plan- any advice?

Hello,

Two years ago I brought a new VW Polo on a finance agreement. When I brought it I was offered a service plan for £124 for 2 services, which I accepted.
Before the end of the first year I was in a car accident and the car was written off. It was replaced by the insurer on exactly the same finance agreement. Now a year on it is due it’s service. The service plan is attached to the old vehicle and I was advised by VW services to ring the finance office and ask for it to be transferred as I still had two services on the plan.
When I rang they refused to transfer the plan claiming it was attached to old vehicle and was non-transferable. I had no knowledge of this and it is not mentioned on any documentation I have. It was also surprising as the new car is on the same policy agreement as the old car.
I have made a formal complaint and they have passed my complaint on to a case manager. I was just hoping for any advice as to my rights in this case.