Terrible service experience. :(

During the trade-in of my BMW - Mercedes Benz informed me that one of the rims on my X3 is a different size to the rest. Upon escalating the finding to BMW SMG Tygervalley dealership, the employee I spoke with confirmed that it is very possible that such a mistake could have been made - during the service of the vehicle a rim from a different vehicle could have been swopped-out and fitted on the vehicle (in error obviously). One would think BMW would act to correct. After numerous emails and no response from the dealership manager the matter is still unresolved.