How can you trust a garage?

My insurance company messed up my mercedi ! They broke the lock of my ignition & then the gsf garage messed me up by destroying my central locking alarm system, they would Not give me my car back!!! It was hell & then I had to get the heavy men in to get it back!! The insurance company wouldn't pay out & they did the work without anyone's permission & in the end my car came back with no radio, no central locking, alarm..how can I trust a garage again!!!