When it comes to having your car repaired or towed, both you (as the owner of the vehicle) and the service provider are protected by the law.
You have the right to good quality service and to have your car properly looked after while it's in the workshop or towing company's possession. If you feel that they have not performed these duties, or worse yet, stolen goods from your vehicle, you have legal rights and can take action.
But you also have the responsibility to pay for the services they provide, and if you don't or can't, then the service providers have a legal right to keep your car until you pay what you owe them, and if you don't, they can institute legal action against you to be allowed to sell your car to make up the money you owe them.
As always, make sure you read the fine print of any contract you sign so you understand the terms and conditions properly, and don't get a surprise later on.