On XXXX XXXX, XXXX cashed a check in settlement of money owned. We received a notice from a creditor, Financial Data Systems, XXXX, that XXXX passed our account to them for collection due to non-payment. Prior to this notice, we received no second or third notice of non-payment from XXXX, and we had no reason to believe after the check was cashed that there was any potential issue with the account or XXXX accounting. We contacted XXXX XXXX on XXXX XXXX, and they stated they would open an investigation and have a superior call us. We contacted Financial Data Systems, XXXX to inform them of the error, and Financial Data Systems, XXXX stated they would await notification from XXXX XXXX XXXX On follow up on XXXX XXXX, no investigation had been started by XXXX XXXX XXXX Re-requested both an investigation and a call back from the supervisor. We continue to be at risk of Financial Data Systems, XXXX filing derogatory payment data to credit reporting agencies due to this error despite being pro-active and aggressive in seeking a resolution. All consumers working with XXXX for medical billing should copy / scan all payments before mailing and keep a copy of the cancelled check ( front and back ) on record. At the time of this complaint, the issue remains unresolved.