Poor customer service / no one can go the extra mile

I have a 2017 bmw 320i f30 which we serviced in November 2019 and service history was loaded on the vehicle idrive. We could view service history on the car idrive system but now all of a sudden all the history is gone. Ive called bmw Montana for a print out of the history because all services wer done by bmw and they advised me that i should contact every branch at which the car serviced. I ask that if they can't view all the service history as the fact that they are using the same system. Montana bmw said they can see Bedfordview history but Fountains bmw can only view they branch service history, mixed answers. So tell me now how am i supposed to sell my car with no service history.