After hearing your brakes make a grinding noise, you decide to take your car to a mechanic. You go to a garage that is offering a great deal on brake jobs. He writes you out an estimate to replace the brake pads, and you leave the car with him. When you return at the end of the day, he submits a bill to you that is four times the estimate. He explains that you needed new rotors, but he could not reach you at the telephone number you left him to discuss the problem. What should you do?