Yes, what you said. I can't pay until they are sure what will be covered. Tests can vary as will the coverage for them. They know I'm good for it. I've paid their other bills on my next visit, but this is the first time I've received two reminders.
Everyone's health insurance seems to be different.
Your post sounds like you might pay an additional amount if your insurance doesn't cover the total cost of your visit. Do you have a deductible that hasn't met the limit & are waiting for that? Otherwise this definition of a copay should fit . Copay is one cost, deductible is another.
Copayment
A fixed amount ($20, for example) you pay for a covered health care service after you've paid your deductible.
Let's say your health insurance plan's allowable cost for a doctor's office visit is $100. Your copayment for a doctor visit is $20.
If you've paid your deductible: You pay $20, usually at the time of the visit.
If you haven't met your deductible: You pay $100, the full allowable amount for the visit.
Copayments (sometimes called "copays") can vary for different services within the same plan, like drugs, lab tests, and visits to specialists.
Generally plans with lower monthly premiums have higher copayments. Plans with higher monthly premiums usually have lower copayments.
Copayment - Glossary | HealthCare.gov
I think in this instance we can use the gov. definition of what a copay is. Meanwhile the doctor has bills to pay so waiting for payment for 4 months is excessive.