Pathetic service levels

Pathetic service yet again from Grand Central Motors. Twice now I have booked installations of the Mercedes-Benz me Adapter, the first time I arrived and they had no record of the booking. The service consultant made me wait for an hour after which he disappeared on lunch and I was told to that I would have to wait until he returned. I promptly left the dealership. Last week I made an online booking and received a confirmation email confirming such. 3 days ago I received a reminder of the booked appointment. Today I get a call from the dealership saying that they are fully booked and that they need to cancel the appointment. This smacks blatantly of a "free" service that is getting bumped so that they can rather slot in a revenue generating customer. The ultimate irony is that I will be purchasing a new GLE vehicle early next year but I most certainly will not be doing so from Grand Central Motors or from Super Group.