You need to use specifics. Saying "they are lazy", "they mumble things about customers under their breath", etc doesn't give management anything actionable. Reporting exactly what happened and what was said is much more effective.

As far as a greeting, I can see how at Subway (where frequently there is a line) the first thing the CSR would say is "What'll it be?" or some other casual "greeting". It is pretty much "Here's your sandwich," and "Next?"