Horandous service 3 weeks later later still no res

My car was in for a bumper repair, the job on the bumper was spot on however we started noticing mechanical issues on the car 1st the warning light on the same day the car was collected, the very next morning a stiff gearbox and on that same day the car came to a complete halt in the middle of the road. We called the panel beater and their response was it has nothing to do with them they didn't touch the mechanical components. Also called discovery explained what transpired and I was promised an assessor will contact me and they will organize a tow service to get the car and get assessed. Its been three weeks nothing has happened I have spoken to at least 5 4 agent of which I had to relay the story to over and over again. to make matters worst today I asked the agent to put me through to someone high in the organization after I was threatened that If they tow the vehicle do the diagnostics and if results show that they had nothing to do with it I will have to pay for it \ tow and diagnostic"even that individual has also disappointed me nothing has happened. another empty promise. Am I being unreasonable if my car went in good working condition and it comes out with issues shoul"""