Double charging the customer

I took my car to Hyundai Roodepoort on the 27th February 2024 for a service. Ever since I received my car back, it has been making a grating sound after starting and driving it. When informing them of the problem over the phone, they told me that there are a lot of mechanics who touch the car, so they cannot be sure who worked on it or what went wrong. Now they have quoted me a fee to bring it in and fix a problem that they created! Why is it fair for me to pay them to fix something that wasn't there when they serviced the car? There is no record of the issue in the service report. This is clearly something that should be corrected under the fee that I already paid for the service. Terribly disappointing customer service.