Job not well done and poor communication

I took my car for repairs on Friday 06th May as instructed by my Insurer. They started working on my car and on the 16th I got a call that my car was ready for collection. I inspected the rear bumper it looked fine, except for the paint chips on both sides of the car. Once I've signed the paperwork and paid the excess I went to check if the jack in my boot is still there and that's when I realized the bumper wasn't properly fitted and there was space between the rubber in the boot and the bumper. I showed this to Thembelihle who was assisting and she got the technicians who then said they have to remove the whole bumper and refit it. I fail to understand how this was not picked up after the whole process including the quality control was completed. I left the car and after a few hours I was told the car is ready and I should come collect it. When I went on the 17th the space wasn't visible anymore so I took the car. I used the car for a day and realized the same space I told the guys about is still there. On Monday 23th May I called Thembelihle to let her know the space is still there and she told me they have to get my Insurance to authorize a new bumper and she said authorization will take up to 48hrs. I got hold of my Insurance and explained the entire ordeal and they've been trying to get hold of Thembelihle to no avail, on Monday and Tuesday. I've been trying to call all morning to get feedback as to how far the process is to no avail and no one is able to assist except for Thembelihle who is not available. I'm so frustrated traveling with a car that's not properly fixed and no one is able to assist