Ask to see the order, make sure it has PCR on it. Then, and this IS the hard part, memorize or print off a copy online of the test tube top colors needed for a PCR test.
When I go to my hematologist, they have a list of the doctors names and exactly what tubes to draw for a visit. My hematologist only does leukemia (maybe lymphoma) and he clearly has his own "set" of tests he wants run on every patient at each visit. So every time I go, I get somewhere around 9 tubes drawn. I go 3 wks early for my PCR draw, so they'd probably only need 1-2 tubes for that, but they still draw the standard set each time. Oh, well, as long as they get the test done right, I guess I don't care about the extra tubes.
P.S. I'd refuse to pay for that test. If the order was written correctly and said PCR, you should be in the clear. Hopefully, they have the record electronically.