No care attitude & demadning extra monies

We took our car to Fast fit to have the breaks and Exhaust done. They changed the exhaust so the car had a better performance. When we got the car back we paid and all was well. My hubby then noticed that the power was lacking from the car when driving. we took the car back. Frikkie and JJ then said they would put the old pipe back on the exhaust and see if would make a difference. When my hubby called to find out if the car was ready and we will collect. They were closing so my hubby asked them leave the car outside. Frikke then went on shouting at my husband saying he must pay for all the extra stuff that was added. That was not part of the discussion and my husband did not say they could add anything extra. anyhow then my hubby got hold of JJ the son. He starts threatening my husband and telling him when he fetches the car he will f*** him up????? he then goes on to tell my husband he will talk to my husband anyhow he feels as him and his dad are the owners and they can do what they want!!!!!! OMG I have never ever dealt with such unprofessional and insulting company ever. JJ went on to tell my husband he will note get the car back unless he pays!!! REALLY!!!!!!