Yep, if you can't trust them then don't bring it to them for a fluid change. This applies to other fluid changes too, like Redline Synthetic transmission oil. Also, regardless of where you have your oil change, always check the oil level before you drive off. I know of two instances where oil was drained but never replaced The quicky oil change place eventually replaced the engine (rebuilt) but the hassle was not worth it.
I prefer to change my own oil - I know what goes in, and the quality. Most quicky places tend to overfill, which may not be good for the engine.