Brought my car in due to a check engine light and ...

Brought my car in due to a check engine light and low tones coming from the engine. Found out the check engine was due to rust around my gas inlet and the low tones were due to low antifreeze caused by a leaking water pump that needed replacement. I had a new ACDelco (OEM) pump put in elsewhere, but my car continued to leak antifreeze. I brought it back explaining that the diagnostic may be incorrect. They contacted me immediately after my inquiry and looked at it again after (no charge) and told me my new water pump was leaking. Seemed unlikely, but I brought it elsewhere for a diagnostic. I was told "the water pump appears to be leaking, but I've never seen an ACDelco water pump leak before." Since it seemed unlikely to happen, a further inspection into the issue was done. It was found the coolant leak was actually coming from the water outlet tube above the water pump and all that needed to be done was a seal and o-ring replacement for the outlet tube. New water pump with labor was around 550$ (about 750$ to their shop do it), their diagnostic was 140$, and outlet tube replacement was 230$. That's over 700$ of things I didn't need, I did include the 140$ diagnostic since that was for nothing, I also included having to constantly fill the coolant. I drive a chevy, so I was hoping they would be very keen on the inner working of my particular car and issue identification. I don't think the proper time was put in on my car. Rough money loss.
On a positive note, I've been there a total of 3 times everyone working there was respectful. They did take my car back in to check it out again almost immediately after I contacted them at no charge. The waiting area is nice, and the coffee tastes great.