Complaint sub-issue: Credit card company won't increase or decrease your credit limit

The complaint I am making today is regarding my Citi Bank Mastercard. I have had this card which started out as a Visa since XX/XX/XXXX and never had any issues with it until now. When I was first approved for the card I had a credit limit of {$6000.00}. Then about 2 years later they increased my limit - without me requesting it - to {$12000.00}. A few years after that came another increase to {$18000.00} - again without me requesting it. And then a few years after that another increase was granted making my limit {$22000.00}. As you will see when reviewing my credit history, I have never made any late payments to this merchant & I have always made more than the minimum payment. I have even paid the card off or at least down several times over the course of 8 years. This is the case in point regarding this complaint. On XX/XX/XXXX, I made a {$11000.00} payment to the card which was almost half of the balance owed on the card - {$21000.00}. Two days later, Citi bank sent me a communication informing me that they decreased my credit limit by almost the same amount that I had just paid toward the card making my new credit limit {$12000.00}!!! I immediately contacted them and was told by the Customer Service Representative that there was nothing he could do and that the decision to decrease my limit was made by another employee in the Credit Review Department. I asked if I could speak with that employee so I could get a better explanation of why such a huge decrease in my limit. I told him that I also just made a huge payment cutting the balance I owed in half and that I paid off other credit cards and loans in order to get my credit healthier. He said that he was not allowed to transfer me to speak to anyone in this department and that I could file a dispute with XXXX which is the CRA that they used to make the decision to decrease the limit. I am not so much upset at the fact that the limit was decreased as I am the amount of the decrease. Such a decrease dropped my credit score which had increased as a result of me paying off a lot of debt. I did dispute the decision but of course Citi Bank reported that what they were reporting was correct and XXXX closed the dispute. I think this is extremely unfair that Citi Bank won't take into account that I have had my account with them for over 8 years ; that I have always been a good paying customer ; that I never once requested any of the increases they gave me and that I always managed to pay the card off or at least make substantial lump sum payments decreasing the balance owed. I can't understand why a certain employee can make such a detrimental decision and than they aren't made available to discuss this decision with a long-time, top-rate customer. I mean if I was a deadbeat would they have increased my limit 4 times over 8 years to reach {$22000.00}?? I highly doubt it! But because they are probably facing delinquency and outstanding balances due to the pandemic they are taking it out on the good customers!! My credit score is still not where it should be because of their decision because it is affecting my credit utilization which would've been much lower had they left my limit at {$22000.00}. I would ask for an increase but I don't want them to do an inquiry on my credit which will drop my score again. Plus I think that if they are going to decrease a cardholder 's limit by half they should call the cardholder to discuss this so that the cardholder is prepared. What if I was going to make a large purchase with this card or use the remaining balance to pay off more debt? I've heard of decreasing a card by a few XXXX dollars but by half is completely ridiculous! They didn't have a problem increasing my card over the years to {$22000.00} but now they have portfolio issues and I'm the one being made to suffer. And I know for a fact that my credit during some of those increases was a lot worse than it was when they made the decision to decrease my limit by half. They wanted me to spend the increases so they could make money but now that they're hurting they are penalizing me!! I just want to get my score where it would've been if they wouldn't have decreased my limit by so much. These card reviews need better rules which will help the cardholder not just the card issuer. Thank you for time assessing this complaint. Hopefully you can help me! ( NOTE : I have attached a copy of the communication regarding the decrease and 2 statements that reflect the previous limit and the lump sum payment made before the limit was decreased. )