Get a written report from another shop
Use this letter-writing tool to complain about a product or service.
Question and answer
What can I do if I’m not happy with my car repairs?The repair shop might not agree that there was a problem with their work. In that case, you can take your car to another repair shop and ask for a written report.
The report could show that the original repairs were not carried out properly, or that the parts provided were not of good quality.
A written report from an independent mechanic can be used to help you prove that the problem is real.
Keep copies of all your receipts, invoices, cheques and card.