Natis and Tax-invoice have a 4 year difference in year model

I bought a car from We Buy Cars (WBC) at the Midstream branch on 2nd January 2020. BMW 320d (E90) it was sold as a 2011 model and the WBC tax invoice also stated that it is a 2011. This car was bought specifically for a customer and the customer paid a deposit and for the balance the customer obtained finance from Wesbank. On receiving the Natis almost two weeks later it was noted that the year model on the Natis certificate indicates the year model as a 2015 (F30) at this time all the defects identified by DEKRA was already done and the only thing left was to register the vehicle in the new owner and title holders names. I made contact with WBC midstream and a certain gentleman in the admin department were very helpful but he could only supply a letter from WBC stating "Please note that after investigating we concluded that the RC1 (registration document foes not state the year model of the vehicle, it only indicates the liability date on registration of a new/FIRST owner" The challenge is because part of the payment of the vehicle is financed by Wesbank we had ti take the vehicle for a DEKRA test which we did. During the DEKRA test there was a number of items to the amount of +- 8000 identified that had to be repaired, which we did. WBC selling vehicles as a certain year model and the Natis certificate then indicate a difference of 4 YEARS is just not acceptable. Nobody at WBC really want to assist in solving this other than pulling up their shoulders saying "You have a problem and We don't know what to do" I do hope that this will be addressed by senior or top management at WBC. Eagerly awaiting their response