Product: Credit card or prepaid card

We apparently had set up {$150.00} minimum payment for our Citibank credit card that was always supposed come out our bank account to pay any credit card balance and had done so some eight or so years earlier. In XXXX of 2017 for the first time since that minimum payment was initiated on the card, our Citibank monthly bill went to somewhere just over {$150.00} per month after we took a 0 % interest offer for an account transfer amount of {$15000.00}, which resulted in a new monthly amount due of {$230.00}, but Citibank apparently could not withdraw any more than the minimum amount and instead charged us late fees for almost eight months, then closed our account. 
Each month the {$150.00} payment automatically came out of our account, as had been done for the previous seven years, so we did not notice the shortfall. They did send emails entitled Account Alert - Explore Your Options, starting XXXX, but all of the emails before that month simply informed us to expect the normal {$150.00} min., despite the fact that the actual bill said we owed {$230.00}, as we later found out. I was not paying attention to the old email account associated with the card, so when they did initiate a warning email, I did not notice it. However, they continued to send me emails notifying me of the pending {$150.00} payment. 
When I finally did realize we were falling short each month in XXXX of 2017, I called Citibank and they would not budge on their position on the delinquencies, saying it had been over 90 days since first notifying us and also insisting that the account payment limit was on my banks end and not theirs. We promptly paid all the underpayments and late fees and asked Citibank to please withdraw whatever the monthly minimum going forward out.Citibank also withdrew an equivalent amount as we just paid them for the past due and late fees, despite are not asking them to this or informing us they would take the action, and instead of a 0 % interest rate on the $ 15k transfer amount, we were charged a penalty interest rate. They also finally started sending emails in XXXX stating that the actual amount owed would be deducted, instead of {$150.00}. And, of course, they sent a report to all of the credit bureaus informing them we had not made payments for eight months. 
Oddly, they did not send us emails every month. Some months it was an alert emails, other months, it was just an email reminding us of the pending {$150.00} payment automatic deduction. And, also oddly, they assessed the {$37.00} late fee about every other month, even though it appears we were not paying in full for every month through XXXX. 
Several more inquiries with Citibank over the past three years to find out why and how this had occurred have not had any results. Recently, I decided to contact our bank and find out when we had put the {$150.00} limit Citibank said our bank would pay, and our bank said we have never had a minimum payment on any account and the Citibank payment authorization had no limit - the auto pay with Citibank was an ACH agreement, as it had been for the previous 27 years with Citibank, and Citibank was authorized to withdraw whatever amount they wanted. Armed with this knowledge, Ive been able to get past the Citibank account reps and talk for the first time to a manager and then a supervisor, and, supposedly, they have finally opened an inquiry into the matter, with the supervisor saying somethings not right with this, but giving no more. This was last week and they say it can take several years to determine what " happened '' and that it would never result in any corrections to my credit bureau record because it has been over 90 days since the first late payment incident. 
While we don't remember setting up the {$150.00} minimum payment with Citibank, it is something we have done with other accounts. We do this in order to pay off the account more quickly than would be done with just paying the minimum the creditor would bill monthly, but we never where informed that, to Citibank, this meant they were not authorized to withdraw any more than {$150.00} ( which they have denied, consistently insisting it must be on our banks end ). But all of the evidence points to the withdraw amount of only {$150.00} being entirely within Citibank 's control. 
Unfortunately, we are apparently powerless to do anything to get Citibank to acknowledge that maybe they made a mistake or, if they do eventually concede some responsibility, correct our credit reports. Is there anything that the CFPB can do for us? Before this incident, I had a spotless credit record, but have since that time paid for a credit monitoring service to help insure that something like this does not go without our notice in the future.