if a company repairs something without my signed permission and extorts me for960$ for it s return are they breaking a law?

A guy once knocked on my door and told me he wanted money as he had just cleaned my windows. i told him I did not have a window cleaner. He said "It's too late, I've done them now" I just pulled out my phone and told him to wait, as the police were going to be interested in him. He was off like a rocket, Not as much money wise but same thing. I can not do repairs to your car, your house or your lawn mower without your permission. You have to request an estimate first, or a person climbing on your roof to check for tile damage, or looking under the hood of your car, is trespassing. You must be told what the problem is and the cost of repair, plus you must agree, before any work is carried out. Tell these people you will involve a solicitor unless they void their bill immediately.

are you saying you gave verbal permission just not a written contract.....call police for extortion

Perhaps. You'll have to consult a lawyer to be sure of your rights.

bigtime. get a lawyer!