Got a Letter from a Debt Collector while My Health Insurance Companies decide who is Primary

During a 2 year period between 2019-2021, I had two different health insurance policies and my providers did not submit on both policies (my fault for not being more aware).

As a result, one has self-audited and found out about about the other in November 2021, and has decided that the other policy is primary. Even more, the insurance company that found out has reversed all payments between that time until the claims are reprocessed through the other policy and the EOBs are sent to them to determine what leftover cost is to be covered.

I’m following instructions from the health insurance company that found out to reprocess claims on the other insurance policies, which just finished only a few days ago (yes, it took between Nov 2021 to Aug 2022 to do that). I’m about to send that now not knowing how long it will take or how they will handle the fact that the other policy has also deemed themselves secondary.

I have filed a Coordination of Benefits to both policies in January/February (though it’s not clear to me if it will help).

In the meantime, one of my providers has sent the now open debt to collections (due to the insurance company reversing payment) while I am trying to resolve it, and my provider has not responded in regards to how I should proceed.

Do I simply attempt to dispute the debt (by phone or mail) and hope that process is enough for the health insurance companies to figure it out? Do I try to explain to the collection company what is going on? I don’t want my credit score/report to be impacted because of this, especially when they are doing this years later when I no longer have them as my insurance.