Mini One 2013 – Dealer has given me 14 inch tires, instead of 15 inch vehicle license

Hello, I bought a Mini One from 2013 last week, 3-door. There are 15 inch summer tires, which were also on it when buying. According to the vehicle registration the car should also have 15 inch tires. There were used winter tires with which I only checked the profile when buying. I did not see that the tires are 14 inch. Today I had the car at ATU, because I wanted to put the winter tires on it. Result: ATU told me it is not possible the Rei What do you think about this? What should I do now? Thanks VG