Complaint sub-issue: Credit card company isn't resolving a dispute about a purchase on your statement

I have disputed a transaction for airfare from XXXX XXXX with Citibank on XX/XX/XXXX, because, according to Master Card " Charge back guide '', the service provided to me was " Not As Described '' ( I booked a flight to XXXX, but was flown to XXXX instead ). 

I was given a conditional credit on my statement, which was then reversed without me being notified. I have noticed the reversal on my statement, and called the bank around XXXX. 
The representative told me that they have a letter to me by mail, to which I would have to respond in order to continue the dispute. They could not tell me anything about the status of the dispute by phone, and they could not send that letter to me by email : due to government regulations '', according to them. 

I waited about 14 days, but the letter never came, so I called the bank again. This time, they said, they would just email it to me ( whatever happened to those " regulations '' this time ... ). 

The email I received contained the response from the merchant, that basically repeated the facts i stated in my original complaint ( they flew me to XXXX instead of XXXX, and said I had to make make my own arrangements from there ), and a note from the bank, saying that, since they got a response from the merchant, I had to provide " additional evidence '' in order to keep the dispute open. I was not sure what evidence they needed, since none of the facts I stated originally was disputed by the merchant. So, sent back my original reservation, and the airline notice of " trip interruption '' as " evidence ''. 

On XX/XX/XXXX ( yes, XXXX day ), I received another email from Citibank, that said they had some " secure '' information for me, and I had to click on some link, and enter my password to read it. 
The " secure '' link they sent had an invalid TLS certificate, and could not be opened safely. When I finally managed to get to the " secure information '', it was more or less the exact copy of the previous letter, saying that they needed " additional evidence '' ( without specifying what fact they needed to confirm ), and that " due to timeframe requirements '' (??? ) I had to respond by XX/XX/XXXX ( within 3 business days ). 

I responded to that email, asking for details of what specific facts they find in question, and require additional evidence for. That email was acknowledged, but never responded to. 

On XX/XX/XXXX, I received an email from them, stating that they found the merchant response " satisfactory '', and that my dispute is now " resolved ''. 

I find this completely unsatisfactory. Not only, this is as clear a situation of " service not as described '', that XXXX XXXX rules promise to protect the consumer from, it is also completely clear from the way Citibank handled this case ( " lost '' mail, lies about " government regulations '', incoherent communication, unnecessary requests, unreasonable deadlines, invalid certificates etc. ) shows without any doubt that it was never their intent to even attempt to resolve this dispute in any other way, which is clearly a violation of their agreement with me as a consumer.