I can also see how people get unknown medical DQ's. Here's my story:
About five years ago, my very young son needed some fillings filled. He wouldn't sit still for the gas, so the dentist recommended that we put him under general anesthesia and have him worked on by an oral surgeon (he was 3 at the time). We made some calls to our health insurance provider and determined that this would be covered.
And it was. He had his teeth filled and capped, we got the EOB's and paid the copayments, and went on with life.
Fast forward six months. We started getting calls from a collection agency demanding that we pay the bill for the outpatient clinic which had provided the operating room and anesthesiologist. Huh?
So I did some quick research on the debt collection laws, figured out what my legal rights were, and asked that the collection agency send us written proof of the debt and that they only contact us in writing (they complied).
The proof of the debt was a statement from the clinic showing the charges which the insurance company said had been paid months before. So we called the insurance company....
....to make a long and frustrating story short, with the help of the insurance consultant who manages our health plan, we discovered that several months after the insurance company paid the bill, they unpaid it. With no notice to us, they reversed the payment to the clinic. The clinic made no attempt to contact us when this happened, just turned the bill directly over to collections.
Apparently the clinic bill had been submitted to our dental insurance, when it should have been submitted to our medical insurance. So we got the clinic to resubmit the bill to the medical insurance, and called the company daily until we got the EOB showing it was paid (which we then sent to the collection agency with a F.O. letter).
The kicker: the medical and dental insurance policies were both provided by the same company.