From 10 to 30 days of waiting

I Brought my car in for minor repair on 13 July 2015, they told me it will take up to 10 days to repair. After 10 days I phoned them to ask when I can come to collect my car. They said that they are still waiting for parts and can't finish my car. According to the insurance company I worked trough, I had to bring it in on the 13th for them to first collect the parts. My car was perfectly able to still drive and was still road worthy. Its know 5 August and they are still waiting for the part. They could have told me to wait before I bring my car until they have everything they needed. In my eyes it is unacceptable to get this type of service. I am currently sending them mail, waiting for a response but to no prevail.