2005 Hyundai Elantra Suspicious Work

Brakes problem
2005 Hyundai Elantra 55000 miles

I went to Precision Tune to get an oil change a week after buying my used car. They said I needed new rotors. They put in new rotors and did a flush, but then since there was still a small squeak, they said my pads also had to be changed. I went back the next week and had them change the pads. The whole job was close to $600.
The next day I went to see the original mechanic who serviced the car 2 weeks before I bought it. They said they had already worked and turned the rotors and they were fine. The mechanic gave me the paperwork in order to show Precision Tune that the car braked were worked on and were fine 1 month before they claimed everything NEEDED to be changed.
I went back to Precision Tune and they are now refusing to give me any of my money back.
Help!