Wrong car on car finance

I will try to cut a long story short, I took out a hire purchase for a car last march, I have now noticed that the car I have been driving is a different registration/colour and model to the car on the finance agreement, I have been told that this is an admin error and they will resolve it once i send them the v5 for the car I am driving, I have done a hpi check on the car I am driving and it shows as free of any finance, is this a good opportunity to negotiate a deal to cancel the finance so I can get another vehicle more suitable for my expanding family.

Any help is greatly appreciated.

P.s I am constantly being told by the finance company that this error has never happened before so there may be some time to resolve this and to keep making payments in the meantime.

James