Couldn't find a better group.

When I delivered, the company that did the blood work didn't get my insurance information from the hospital. They kept sending the bills to my old address and ended up giving it to a collection agency. I disputed it and they took it off credit bureau reporting. I got an evidence that I had insurance back then in 2016. How do I get it off the collection agency? The insurance company may deny saying it wasn't billed on time but how do I get myself out of this mess that I didnt even know I got into for no fault of mine??