My son had his van broken into recently, the thief put a hole in the door and undid the lock through this. The van was fixed at a local garage through his insurance, but they didn't replace the lock, just the doors. He went to work and during the day he noticed that the lock wasn't locking every time. He went back to the garage but they said that no one was there to deal with it, so it was agreed they would get back to him. However, they didn't. He phoned his insurer and they contacted the garage, but the garage aren't taking responsibility because they say that the lock was working when it left the shop. What should we do?