Unauthorised repairs

Good morning. We took a car to VW in East London and after their assessment and report to the insurance, the insurance only approved for certain parts. We then told them to repair what has been approved by the insurance. But they fixed other things and they don't want to release the car, saying we must pay for other things they have repaired. I have been asking them to show me an email where the authorised to carry out those repairs but they can't.