I got a surprise collections notice of a copay I was told I didn't need to pay over two years ago. How do I keep this from hurting my credit?

A couple years ago I went for cardiac testing following an incident of tachycardia. When I went for one of the tests, the front desk staff told me that since it was a test and not an office visit, the copay probably didn’t apply. I vaguely recall getting a bill for the $40 shortly after the visit, but hadn’t received an EOB so I figured it was still going through insurance. That was two years ago.

The other day I got a statement that my account was going to collections because the $40 is past due. I never got another bill after that first one, so no news is good news, right? Now this could hurt my credit just as I am planning to buy a house next year.

I am lucky that $40 is a minor amount at this point in my life – I’d have paid it immediately had I received a second bill. It frustrates me that such a tiny thing appears to have lowered my credit score.

Do I just write a check to the collections company, or is there another way to approach this so it can be removed off the credit report?