Things that make you go huh?

So I have been working with the kids' Dr office for about 2 months on a $20 copay charged when I took the boys in for well child checks last November. Will had a $0 balance but Nic kept getting billed $20. So I called again today and the billing lady said that basically we were charged an office visit when I brought up a potential that Nic may have some allergies. These "allergies" make him uncomfortable when he tries to go to sleep all congested so I talked to the new DR and was looking for a suggestion. He shared that if we tried over-the-counter allergy meds regularly for a month then go off of them we'd know if he had an allergy that was treatable OTC and would not need to follow-up in the office.

Well, apparently that cost me $20 and who knows how much Blue Cross Blue Shield was charged. I am just shaking my head and trying to understand how bringing up this topic at an overall well-child check constitutes another additional charge. Any thoughts?