First, talk to the person in charge. If you can't agree on a fair solution, tell that person that you will have to take your complaint to the next level and then do it.
Before escalating your efforts get a second opinion. If other mechanics have a different diagnosis or agree that a job wasn't performed or priced properly, it can support your case.
Put everything in writing - whom you spoke to, what happened and when. Keep copies of all receipts, written estimates and correspondence. Keep letters and emails short. Recount the facts of your problem, with exact dates and details. Include your car's year, make and model and all your contact information. Specify what you want, such as a free repair or a refund. Make it clear you expect a timely response or you will take it to the next level.
Escalate your complaint by taking it to the owner at an independent shop and contact the company's customer service if you're a chain store.
If you're still not getting anywhere and you think that you're been defrauded or misled, take the issue to your state's consumer affairs or consumer protection department. Do an online search for "car complaint" and the name of your state to track down the right agency.
Get the word out to your local Better Business Bureau or Chamber of Commerce and ask how you can lodge a formal complaint if you still haven't made any progress. If you're the victim of egregious abuse, call your local radio and TV news stations to see whether they want to do a story.
If all else fails you might want to consider filing a suit in small claims court, where damages are limited to a few thousand dollars. Court fees are moderate, generally $50 or so, and you don't necessarily need a lawyer. You will have to show that your claim is valid and be able to thoroughly document it. Filing a suit in a higher court more than likely will not be worth the expense.
Jody Rohlena & Erika Wortham