Does not cover shortfall

Went in for a G-scope. With authorization. Doctor did not get pre-authorization for 1 item . Bonitas confirmed the amount not paid was reflected on the statement via e-mail. Paid the Doctor the amount and sent it through to Stratum. Stratum said they will not refund this amount, because Bonitas did not specifically note this amount on their monthly statement even though Bonitas confirmed the amount and where it is reflected.

Question: I pay for GAP cover to cover any shortfall. This was a shortfall. Why do you not want to pay?