i have the same experiance before, but with other garage, since u have a rent a car try visiting the garage everyday to push them and work very past. I know its really a waste of time but that's the way you can do to push them.

It is a normal practice by every garage to pending some works if your not showing them that you really eager to finish it immediately.

everyday customer is coming to them and whenever its minor works and willing to wait they will work it and finish it first.