If you have a written estimate, you are good to protest the charges with the CC company. When it comes to estimates, they can only exceed the estimate by 10% without having you sign and agree to another written estimate. So , if I read your post correctly, the estimate you signed was for $1500. They can only legally charge you up to $1650 without your legal written consent.
Tell the credit card company that they padded the labor charges, could not provide any invoice(s) with itemized labor hours, and that you are NOT satisfied with the labor work. Furthermore , tell them they were holding your merchandise hostage and threatened to sell your merchandise if you did not pay the outrageous bill.
Screw them, just like they screwed you.