Product: Payday loan, title loan, personal loan, or advance loan

I processed a payment through my online bill pay service at my bank on XX/XX/XXXX for XXXX to pay most of the balance of approximately {$19000.00} on an installment loan at Citibank, with the payment due on XX/XX/XXXX. The pmt was mailed XX/XX/XXXX. On XX/XX/XXXX Citibank contacted me saying my loan payment was past due. On XX/XX/XXXX I stopped payment on the check and I issued a new check for XXXX through my bank 's online bill pay service to replace the previous XX/XX/XXXX loan payment that Citibank said was never received. Additionally, I had my bank process it as an overnight payment and it was sent by XXXX overnight letter to Citibank 's overnight payment address in Arizona. XXXX proof of delivery shows the payment was received at XXXX am on Fri XX/XX/XXXX. The check was deposited on Mon XX/XX/XXXX and cleared my bank account on XX/XX/XXXX. Citibank has never posted my payment to my loan. In the meantime, Citibank proceeded to post and deposit the check I stopped payment on because they said they never received it on XX/XX/XXXX and it was returned to them on XX/XX/XXXX. They have never posted my replacement check to my loan account, which cleared my account on XX/XX/XXXX. Their abysmal customer service can only look up my loan in their system and tell me nothing has been posted. No one seems capable of simply looking up my payment and posting it to my loan account. I have talked to XXXX customer svc reps and XXXX supervisors. I called and asked for Mgr, I Talked to XXXX XXXX XXXX my XXXX phone call with XXXX. XXXX couldn't simply research my pmt in their system and gave me a Fax number because they still don't use email, as well as the call back number. XXXX said If I just send a copy of the cancelled check they could adjust my loan account. I faxed the cancelled check and the Overnight Proof of XXXX twice from XXXX diff Fax services who both confirmed it went through. XXXX said it should be posted in XXXX hours, by Thur. My payment Still was not posted by Citibank as of Fri XX/XX/XXXX and the loan continue to show past due while interest accrues daily on the unpaid balance. I contacted another customer Svc rep at the call back number XXXX gave me on Mon XX/XX/XXXX which appears to be a call center in a XXXX XXXX where it was difficult to understand what was being said. That customer service rep gave up and I called back again and asked for a supervisor. The supervisor was difficult to understand. I gave her all the details and said I'm looking at the cleared check, what info do you need to find my payment. She said to give her XXXX to receive the pmt, to which I again said the pmt was already received by Citibank and cleared my bank account. I have faxed the check and proof of delivery to the fax number XXXX provided XXXX more times today on XX/XX/XXXX because the payment has still not been posted, even though XXXX came out of my bank account on XX/XX/XXXX. All XXXX faxes were confirmed as transmitted successfully by the fax services I had to use because Citibank still only uses fax machines, which no one uses anymore. They could not provide a customer service email address or a way to upload on their website my cleared check and proof of delivery to their customer service dept for the payment that cleared my bank account.