They probably have a pair of lipped discs in the back for when anyone asks to look at them.
Yours will be on eBay tonight.
I agree with wwaswas, you didn’t authorise it. Put it back together and go for a 2nd opinion. They charge you twice the going rate anyway at a main dealer.
Are they offering free pads for the life of the car like another company are?
Threaten them with an engineer report and tell them you will report them to the office of fair trading. See what they say.
Remember the customer is always right.
If that fails come out with my favorite line of all time (which should only be used in circumstances like this) “can I speak to the top dog please, not deputy dawg” it really pisses people off.
Btw, now you have vented, do you think that they might have been lipped?