Service done om my vehicle

I took my car in my a service on 08/11/2021 at Ford Fury Amanzimtoti. The service I received was very professional. I was dropped off at home and also picked up again after my car service. When i receive my car back the afternoon, I could definitely feel that the service was done. However after a rainy day and me trying to see through my window, the wind coming out of the air-con wasn’t cold anymore. Where before my service the air-con worked 100% and made the whole car cold. And now the wind coming through is not cold anymore. I then took my car back on 24/11/2021 for them to check seeing that it worked before the service. I was then advised that in order for them to check the air-con, i have to pay R1400 for a diagnostic assessment to be done. Reason being that they did not do anything to the air-con when my car was serviced. However i feel that this is not fair to a client to have to pay for something that worked perfectly fine before they serviced the vehicle. I am very disappointed in the service I received and makes me worry for when I service my car again if something else will stop working as well.