Personally we notify them and ask what they would like us to do (send a refund check or wait for them to retract, or whatever). If they do not follow thru (if it's something they need to do) then we call back a second time. If still nothing, we call back a third time. Each conversation/interaction we have is well documented with who we spoke with and what we were advised. After the third time, if the action is required on their end, we do not continue to follow up. This is only if it is not a situation where we can mail a refund check. If we are sure of the overpayment and know WHO gets the refund and the exact amount, then we advise the provider to mail the refund check (which they give to us and we mail with documentation). The only case that we let it go is if we believe it was processed incorrectly, but are not sure of the exact outcome and need the insurance carrier to review the claim. Or if the insurance carrier doesn't accept the refund check for whatever reason (which it has happened).