I'm sorry you are going through this. I suggest you take the following steps:
1. Contact your insurance company to appeal their decision. They have a formal process for reviewing decisions. Keep all correspondence in this appeal.
2. Contact the company who provided the scan and notify them that you are appealing and ask that they halt collections pending the appeal. Include any documentation of the appeal including the insurance company's time frame for resolving the issue.
3. If the insurance company upholds their original decision you may continue to appeal but the mechanism depends on whether you have an employer sponsored plan, Traditional Medicare or Medicare Advantage. If an employer sponsored plan or an ACA plan then I would recommend copying your State's insurance commissioner.

It is a bureaucratic process by design but you can get a good result.