I'd be surprised if you made any difference. The biggest car dealerships have been untouchable for so long they can do anything they want these days
We had an VW with the 4motion technology come into us with a transfer box that had seized while the guy was driving it, seemingly this oil is meant to be changed within 40,000 miles. The car had a full VW dealership service history, and had done 42,000 miles. VW are holding absolutely no responsibility for it though despite telling a previos owner they'd done it in one of their services and now we're left to pay for the repair (the box itself is £1500) as we'd just sold it and it was still under warranty. AC aren't the worst at all, they're just less sneaky than the Audi and Ford garages of the world