Product: Credit card or prepaid card

I recently learned that CITI Bank closed a credit card account ( without written notice ) that was issued 26 months earlier. 
My credit card account status was current, paid up to date, with no late payments ever, all pervious payments met or exceeded CITIs minimum required payment credit card repayment requirements. All payments were made XXXX weeks before payment due. 

In short the account is in excellent status, and each payment paid was paid early and above the minimum payment requirements during the entire length of card holder agreement. 

I routinely make my credit card monthly payments thru CITI bank automated ACH debit system. The system is an automated technology that allows paying your credit bill via your person checking & savings account. The account was linked together using CITI bank account service. 

I used CITI Cards system with the same banking account information to pay my credit card bill the pervious month without incident or concern, and for that matter tI have paid by ACH everytime since becoming a Citi customer. As is the case with all my reoccurring ( eletrical, internet service, auto insurance..all paid without flaw using ACH and my personal checking account. 

However XX/XX/2021 payment, CITI card system indicated my payment was returned, I was charged {$28.00} for return fee for a ACH return. 

While I knew I had the resources in my personal bank account to cover the amount of the authorized payment..CITI states my payment was returned without explanation.

Upon receiving the non payment email I immediately contacted CITI Cards via chat on the CITI App and inquired about the returned ACH. I was advised that the routing number appeared to be incorrect. I was advised to correct. I was advised the {$28.00} removed if I make a request.

After the inquiry I immediately again made payment using CITI Cards service, I removed the old account that was used successfully before and linked the same account again to CITI Card payment platform for ACH payment. And again the second payment attempted failed.

I contacted CITI Cards again, a second time via phone and inquiried as to why my payment is being rejected and why Citi credit card closed?

I was advised my credit card account was closed due to breach of terms due to my payment being returned!

I tired to explain the situation, the customer service rep was indifferent..was not in his department?? I gave him an ear full and disconnected the call.. 

My account was closed due to CITI Cards technology failure. For the I used the same bank account information for XX/XX/2021 XXXX the pervious month ), as I did for XX/XX/2021 payment ... both times the payment was successful and completed using the exactly account information, same method ( ACH ) ..its Citis technique glitch. 

After collecting evidence that nothing has changed on my end and using the same methods I went further I contacted my credit union for where the payment was being pulled to discuss any technology issues, any account issues..was there ANYTHING to prevent the authorized CITI Cards transaction from occurring and being completed XXXXNO XXXX XXXX, there sis no reason Citi Card didnt receive your payment. There is NO issues from XXXX XXXX side what do ever. That evidenced by the fast all other authorized transactions were processed in a timely manner.. 

The bottom line, I did not breach my service agreement with Citi Cards, I was not in default, I paid my debit on or before due date, I pay the required due amount or greater. 

Please note the attached doc indicating how the authorized ACH was successful the pervious month, with the same bank account, same method of transfer. This is purely a CITI Card error.