Poor services rendered by Kia Tygervalley

I've taken my car for a service at Kia Tygervalley Service Centre on Thursday, 24 Nov 2022 & later the day the dealership let me know that the car will only be done the next day as they have to see to the cambelt. I waited all day on Friday for the call & when I contacted them myself on Saturday morning I was told that the car is done. I went to collect & it didn't seem like it was done but they were rushing to get the car to me. I am genuinely always just give everyone the benefit of the doubt & let it go.

On Sunday morning I noticed a big oil leak from the car which has never been there prior. It was still quite bad on the Monday.

I contacted Kia Tygervalley & was told that I had to pay R800 & odd for a diagnostic. I am simply returning the car to the service centre to check if all is in order as this fault did not occur prior to the service so why is it that I am liable to pay for a diagnostic service now? I am certain that something must be wrong that occured during the time the car was in service. I was contacted twice whilst the car was on service requesting for additional costs for faults found but none relating to oil leaks.

Please explain so that I am able to understand how services are rendered these days.