Software problems of the 2017 Audi Q7

While driving down a local city street, the car began to lose power, flashed a bunch of error codes and then lost power within a few seconds. The steering wheel locked when this happened so the car could not safely be steered off the road. They did initially replace the battery thinking that that was the cause but it happened shortly after leaving the mechanic so it we took at back which is when we were told that a software update was needed but that only the dealership can do this. The car is now sitting at the dealership but that are now telling us that we must buy their battery otherwise they can't work on it.