Before doing this, you should know about the Repair and Storage Liens Act. Under this legislation, a repairer can keep a vehicle and sell it if a bill is not paid.
If you find yourself in a dispute and don’t want to pay what is demanded, your best course may be to make an application to a court and pay the full amount of the bill there. When you do this, the repairer is required to return your vehicle to you. You can then make your case to the court, leaving it up to a judge to decide how much, if anything, the repair shop should be paid for the work.