GROUPON PURCHASES BEWARE!!

GROUPON PURCHASES BEWARE!!
My first time in here. I booked an appointment to drop off for oil change before 2 weeks. I got a Groupon coupon and while booking my appointment, I informed this to some lady over the call. She asked me about my car, make and model and said that my car needs a synthetic oil change and I purchased for a regular one. It could cost me $20 extra. I said OKAY and booked it.
Finally, after 2 weeks, I went to drop off my car and there was a man at the service center who said they cannot take my mini cooper inn. I was requesting why and trying to tell that I waited for the appointment and got confirmed that my coupon would work. he may be in his 60s age. He was replying back rudely saying " It needs eyes coz it is clear underneath the coupon that we accept for toyota and nissan only". I may not have eyes but my ears are not deaf. I confirmed after talking to the lady. I was ready to pay $100 for my oil change coz its already over the mileage and am desperate. I asked him if I can come around 5.30 - 6pm to pick my car. He was again rudely saying that " Our gates will close at 6" why cant he be little nicer??? What did I do to him?
This is kinda weird. Spending my money and getting rude answers in return. I will never ever visit this place.
overall satisfied but it would be nice if they inform me to change my filter. I go for firestone usually and they will call me before taking any action with my car.