exhaust leak

I brought my car to Allway Auto for exhaust leak. The owner told me that he can fix it for $250. I left my car and left. About one day later, he called and told me that the bolts were very difficult to remove. He had already spent more than 10 hours on my car. He wanted me to give him $200 dollars more. In order to get my car back, I had no choice but pay him what he asked. He only accepted cash. I received a hand written receipt. No detailed description about what he had done. I really doubt what he said. I do not recommend this shop for car repair.