AutoNation Chevrolet Laurel

I bought my 2008 Pontiac Grab Prix in for a "clunk" in the front end. After having my car for five hours, all I was told was my transmission fluid needed to be changed. What has that got to do with the problem I bought it in for, and why wasn't it checked out? I even took the car in early to be looked at. Five hours from a GM certified mechanic and they found nothing and were more then happy to charge me $200 for my troubles