Product: Credit card

my XXXX XXXX Citi Card account received a payment by United States Postal Service money order from me on XX/XX/XXXX that they never posted as a payment to my account in the amount of {$990.00}. I have made non-stop efforts almost daily trying to get them to research the missing payment and post it to my account to no avail. I obtained both a letter from USPS verifying the money order was cashed on XX/XX/XXXX and they sent me a processed copy of the money order cashed by Citi Card, as shown as stamped by them on the back of the money order. On the front of the money order Citi Card employees hand wrote my full account number, the date of XX/XX/XXXX and the amount of {$990.00}, yet they never posted the payment to my account. I have called Citi Card almost daily since late XXXX to no avail, sometimes spending as much as 45 minutes on the phone seeking but receiving no help. I sent written letters with supporting documentation on XX/XX/XXXX and XX/XX/XXXX including PROOF of the {$990.00} processed payment received by them on XX/XX/XXXX but not posted to my account. I have sent the Citi Card payment department, citipayments@citi.com direct emails showing PROOF of the payment. I have sent them more than 6 emails and have had no response and no correction to the fact that they have had {$990.00} of my money for two months and have not applied the payment to my account. In my near daily calls I can never get anyone in the United States but geXXXX XXXX customer service that is generic and unhelpful. I can not get a direct line to the payment department or even anyone in the United States to talk to. Some customer service reps overseas put a " conditional credit '' on my account but then it was removed and the {$990.00} put back on my account the same day. One investigation into what happened to the {$990.00} payment was closed out because they found my " payment for {$990.00} posted on XX/XX/XXXX ''. NOTE THAT ON XX/XX/XXXX THEY RECEIVED TWO US POSTAL SERVICE MONEY ORDERS IN TWO SEPARATE ENVELOPES. ONE WAS FOR {$990.00} AND THE OTHER WAS FOR {$990.00}. THEY ONLY POSTED THE ONE FOR {$990.00} and consistently show an inability to process the fact that these were two separate payments in two separate dollar amounts. I tell them this every time I try to communicate with them, to no avail. To date they have refused to correct the error, refused to allow a temporary conditional credit to my account for the missing {$990.00} and it caused my account to be overlimit on my credit report. Customer service even refused to put the temporary credit on in spite of being advised that I emailed and mailed the payment department absolute proof they received the payment on XX/XX/XXXX by providing them with a copy of the money order that was clearly received by them on XX/XX/XXXX and processed on XX/XX/XXXX. My credit score has now been damaged with an overlimit report. Ironically today Citi Card sent me an email asking me to update my annual income based on my account being overlimit, when it is only overlimit due to their belligerent negligence. Citi Card failed to properly post this payment on XX/XX/XXXX. It is one thing to make that mistake. It is quite another thing for the extraordinary negligence of this company since that time to correct this mistake. They have put me through an excruciating nightmare and I spent several weeks worried my essentially {$1000.00} was lost in the mail and would never be recovered. The failure to correct this error for a payment made two months ago is not only inexcusable but unforgivable. I have experienced nothing but incompetence and indifference about this. NOTE that my normal email is XXXX and that is the email address I communicated with them at. When trying to file this complaint CFPB said I already had an account at XXXX but I didn't remember my password and I was not getting sent an email to reset my password, so I am doing this through XXXX but I also prefer being emailed at XXXX where all my communications are with Citi XXXX.