Car Finance Dispute

KPM1996

Hi,
Almost 4 years ago I took a car out with a dealer on finance. This was a monthly payement with a balloon payement at the end if I wanted to purchase the car as my own. This was due in February 2020. 4 months early the dealer called and invited me in to talk about my options where I explained I wanted to part exchange the car providing I was in positive equity (which I was) and purchase outright from them a new car. They let me look around and I found a car I wanted ect. The contracts were drawn up to show the calculations of settling my finance and part exchange ect. I went through this contract twice with two different people each time and paid the full balance. 2 weeks later they come back to me telling me they calculated the incorrect finance settlement figure and stating I owe a further £540 to cover this difference. However I do not see why I should pay as I and they signed a contract agreeing to the prices based upon their judgement and knowledge which surely is binding? Surely they cannot come back once all is done and dusted and I have my car they have my money? I also do not have an extra £540 and they asked for it like it was nothing!
Any advice would be very helpful please.

[Deleted User]

If they made a mistake, then it can be rectified.

If you cannot pay it in one go, then ask to pay in installments.

Clive_Woody

Offer to return the car and ask for the finance car back for the remainder of the contracted period. See what they have to say about that.