Brought my custom built desktop in for overheating...

Brought my custom built desktop in for overheating issues. I told them exactly what I thought the problem was and what I was looking to do to fix it. They said I needed to let them run a diagnostic for $30 and they would call me in 2-3 days. I called on the 3rd day to find out it hadn't been looked at yet and they were going to do it right then and call me. No phone call, so the next day I went to just get it back from them. They tried telling me it wasn't overheating and my OS was crashing and might need to be reinstalled. They also tried saying that it being overclocked was a part of the problem. They also lost the screws to my side panel. Nevermind that it was just sitting there with the panel off, I had to clean it as soon as I got home. They have no clue what they're doing when it comes to pc builds and repairs, and just hit you with that diagnostic fee and try to scam you. Btw, the problem turned out to be exactly what I thought and I need to replace my Liquid CPU Cooler and just for extra assurance upgrading my intake fan. Oh and saying overclocked at only 10%, when the machine is capable of 30%, is a joke. Just goes to show if want something done right, do it yourself.