Insurance reversed payments to provider

I’m a patient, and I saw a counselor for about 8 months about 2 years ago.

At the time, I had insurance A.

At some point during that time, I got another job with Insurance B.

Insurance B didn’t cover the therapy sessions, so the provider just continued to bill to Insurance A.

At some point, after I finished 8 months of therapy, Insurance A did a reverse on most of the payments made for those sessions, for reason being coordination of benefits (I had no clue what this meant until now)

Anyway, I was out of country for some time, and my provider wasn’t able to reach me regarding this issue.

When i came back, I got a bill for over $1000 from my provider.

I told my provider i can’t pay that, and why did they continue providing service after the first claim was returned.

Provider said I should have called my insurance to resolve.

I called Insurance A and they said that provider should have called them to resolve.

Because so much time has passed, insurance A won’t pay out anything.

Whose fault is this? Will my counselor still get paid? – he was actually very good…

I obviously wouldn’t have continued therapy if my insurance wouldn’t have paid.

Any thoughts?