My Easter holidays spoiled by dent boyz

Went to Dent boys to fix a bumper to my Mercedes Benz C220 CDI, 2009 Model. there was a minor scratch to the bottom of bumper, first it was partly fixed just at the dent bad workmanship,then I was promised that they will fix it, which they claim they have,but that's was just the beginning. my car does not start anymore,Morne called me and I called the guy at Mercedes and i was told to go there with my spare key as they might have decoded my key as they did not take off the terminal of the battery when stripping it, got there with my spare key, my car still did not start. was again advised to bring the car to Mercedes as futher testing might make more problems i offered to send AA to their workshop to take it to Merc, Vall said it would too costly they insisted on calling their own electrical technician, who could not fix nor diagnose the problem. they finally called a guy from Mercedes, now am still in JHB with no car, they have not got back to me with a temporal solution (courtesy car),as I have taken time off work to go home to kzn for Easter holiday.Morne acknowledged that the problem was theirs but has since not gone to work, Frustrated.