Product: Debt collection

This is related to a previous complaint that we filed against XXXX XXXX ( XXXX ). This involves a XXXX bill for a cancelled contract of {$350.00}. Because the bill from XXXX was questionable ( i.e., the contract had 10 days left and they originally told us that we would not be penalized for breaking the contract but later billed us ), we believed we were in the process of working this out with XXXX. However, they turned the debt to a collection agency ( DCI Collections ), and we immediately paid DCI the full amount and have an email receipt ( from XX/XX/XXXX ). However, DCI contacted us about XXXX months later again seeking payment. Apparently, the account # was XXXX digit off when we paid so it was not recorded as paid. We sent them the email receipt, and, although we received no acknowledgement, we believed the matter was resolved. However, we later received the same bill from another collection agency. We sent the receipt via snail mail with an explanation, and requested a letter confirming that the debt was resolved. We received no such letter. On XX/XX/XXXX, we again received a debt collection letter from XXXX XXXX indicating the bill is not paid. We filed a complaint with the Consumer Financial Protection Bureau, and we attached the email receipt showing that we paid this account in XX/XX/XXXX, with our submission. After receiving notice from CFPB, XXXX XXXX dropped the account and apologized for the inconvenience they caused us, and they advised us to contact XXXX. We immediately contacted XXXX, and unfortunately have not had much luck with this. Our two attempts to discuss this with XXXX result in employees telling us they can not help us because the bill has been " passed on to other departments '', and they transfer us to other departments that are no more helpful. On XXXX, XXXX XXXX, we were told that we would receive a return call from the XXXX financial department in XXXX hours, but we received no such call. Finally, on XXXX XXXX, we called XXXX and demanded that they connect us with someone who could help us with this issue, and we were automatically connected to XXXX. The agent sent us an email and asked us to attach the receipt showing that we paid the bill, and he assured us that we would hear something in XXXX days. I emailed again on XXXX XXXX asking about the status of this issue, and I received no response. I called XXXX yet again on XX/XX/XXXX, and was directed to a supervisor ; the supervisor called XXXX while I was on hold, and I was told that they were looking into the matter and I should get a call from them in XXXX minutes. I never received a call. Yesterday, XXXX XXXX, I spoke again with XXXX and was informed that the real issue is that DCI Collections is continuing to deny that they received a payment from us, despite the fact that we have a proof-of-payment email from them. XXXX is going to try to contact XXXX Collections one more time about this matter, but we are simply just fed up with this - it should not have come to this when we have provided proof of payment. We believe that we are justified in filing this complaint and that there should be a record that this company collected from us yet did not report the account as paid. 
We believe that DCI should have to answer for the fact that they collected {$350.00} from us and yet never reported the payment to XXXX. What happened to these funds? 

We have attached the email receipt showing that we paid this bill as a word document with this submission.