Product: Credit card

I had a Citibank Mastercard with a XXXX limit that I had completely used up and I was slowly paying it off a little each month as I have many other bills and I can not afford to just pay off the entire balance all at once. in the app one day I was making a change to the autopay feature and I somehow and completely unintentionally set up Autopay to pay off the whole balance due on the card each month. I intended to setup autopay to pay some amount under XXXX a month, a little more than the minimum payment. I realized I had made this mistake when one day I looked at my checking account and it was overdrawn by {$1300.00}. 
Citibank had attempted to pay themselves {$1800.00}. This was a result of what I had done on the app without realizing it. I immediately contacted Citibank and told them what happened, apologized for the mistake and explained that I never would have intentionally created an autopay for the full balance due since I had no where near that amount in my account and it had only just happened that day so they said it would be reviewed and they would be in touch with me to let me know if they were going to reverse this charge and send back my money. So next I called the XXXX XXXXXXXX XXXX where the checking account is and their explanation was a little Different as they acted as if I had nothing to worry about as the money was never transferred to citi and assured me it would be back in my account by the next day. It was back in my account the next day, but the day after that Citi once again attempted an electronic transaction to get the full balance owed from my checking account. The same day I received notice that Citi was lowering my credit limit to {$600.00}. After one more failed attempt to remove {$1800.00} from my checking account that was at the time down to a balance under {$200.00}, Citibank finally stopped that transaction from happening and with fees and interest, etc. my citi app showed the card now had a balance of {$2300.00} and that I was over my new lower credit limit by {$1700.00}. Soon thereafter the app indicated that my minimum payment due on XX/XX/17 would be {$1700.00}, the entire difference between my already existing balance and the new lower {$600.00} credit limit. I contacted citi and was told there was nothing I could do but payoff the whole amount over the {$600.00} limit and if I did not then citi would start adding {$40.00} a month as a penalty fee for exceeding my credit limit. So, because of the mistake I made with the app, it seems I am about to get seriously penalized by Citibank and their reps I spoke to didnt seem to think it made any difference that I am only over the limit because they retroactively lowered my limit and I have not engaged in any transaction that caused my account to be over the limit, I am only over the limit because they lowered it. They wanted to explain the reasons why my limit was lowered but that was really not the point, although I am certain they only lowered the limit when they thought momentarily that I had paid back {$1800.00} and lowered my balance to {$600.00}. I just dont think they should be able to lower my limit and then demand immediate payment of the entire difference, {$1700.00} as the minimum payment, which will if not paid cause them to add more penalties to the balance making it even farther over the limit. I mean can they just lower my limit to XXXX  and demand all their money right now? They seem to think they can.