If I have a debit card and used it, or a credit card to dispute a charge?

If you already think the person can't fix it, then take it to someone else. When you sign the papers to get your car back and pay for the job, you are agreeing that the job was done correctly. If you think that your car was not properly fixed, get proof by bringing it to another person and then sue the first guy. You can get into serious trouble stopping payment on checks, and disputing credit/debit card charges for the wrong reasons. Typically the dispute feature is only for fraudulent charges. Some banks/credit cards offer guarantees on purchases and will give you your money back, but you would have to check with your specific card (call customer support number on the back of your card) to see if your card is a part of that plan and if it covers your specific situation.