Product: Credit card

Citi Bank XXXX Costco Card Note, I try to use the card Three times after being told that the situation was fixed. 
I answered, the company did not give me the information because they actually gave me three different reasons for the decline, none of which were satisfactory. The lady XXXX, mentioned below, was going to give me perhaps a fourth reason for the decline, To which I replied that I wanted it in writing. She refused, and thats why I decided to come to you people as my last resort. 
XX/XX/XXXX, submitted application and credit card payment to XXXX XXXX XXXX for a travel visa, submission payment declined for incorrect information. Spoke with supervisor who tried to correct the system. She thought the air might be the last XXXX digits of a XXXX digit ZIP Code so she removed the last XXXX digits. She Try to help and said they would send me a letter of explanation that I was indeed, correct And shouldnt have any more problems with the card. 
XX/XX/XXXX, Didnt receive the letter, submitted payment to the XXXX XXXX XXXX XXXX submission declined. Spoke with supervisor who refused to accept my information. Supervisor, decline to send me a letter until I threatened to go to the sponsoring company, Costco, and raise XXXX at which time they said he would submit explanation letter explaining what happened to me. Again, never received it. Of course, I tried to use the card again assuming he had double checked everything. 
I never got the letter from either supervisor so I called back again, I believe it was on the XXXX XXXX I was told that the recipient of the credit charge, XXXX, kept refusing it, because of incorrect information. Supposedly, it was XXXX fault. 
This was not my error as I double checked my card number, expiration date and three digit code each time I attempted to make a charge. I am old but not stupid. 
To clarify, I was dealing with the XXXX XXXX XXXX in Washington DC NOT a travel agent, for the purpose of acquiring a visa to travel, XXXX is one of the largest banks in XXXX. As an aside, since XXXX to now, my statements showI had spent {$14000.00} using this same credit card. The fee for the XXXX XXXX was {$40.00}. 
Im not gon na get into the gory details, but I can tell you that after a minimum five+ hours of conversation With supervisors from Citi Bank , I was frustrated. I had heard XXXX different stories on why the charge did not go through, relying on all of them and resubmitting my card. I had spoken with XXXX XXXX at the XXXX XXXX XXXX visa section and told her of my difficulties. Finally, on the fourth day, I pulled out another credit card, which of course went through and also canceled the above numbered card and ask for a brand new one with new numbers, new expiration dates and new information. The person I spoke with on my reorder I believe was named XXXX, a lady, who was very cooperative And helpful. As for the two supervisors that was supposed to be helping me, I thought I was speaking to robots, smug robots at that. 
My last conversation with Citi Bank was this afternoon when an additional supervisor name, XXXX called me. She wanted to explain the whole thing however, in our last conversation, I was under the impression that I would get something in writing. I told her that the time for verbal explanations was long past and she had intimated I would get something in writing. The situation had progressed from just a mistake on a credit card by whomever to one of broken promises and bullying. I told her that if she wanted to explain what it happened, to please send it to me in writing, and she said she could not send anything in writing. Thats when I told her that I had to spend a minimum of five hours and probably a lot more hearing several different stories and then if she could not give me something, As intimated in our last conversation, that I had no time for her. 
The word that most applies in my mind to the way I have been treated by this massive financial institution is abusive. 
Costco appears to have done everything they could for me, all Im asking for is a real explanation in writing as to what occurred so that I can send it to the wrong XXXX XXXX, so they will understand why my credit card was turned down three times in a row. This has been a hardship and a personal embarrassment. I am a XXXX XXXX, having had XXXX XXXX XXXX of last year, and several years ago, I was opened up for a XXXX XXXX. 
I own a condo, and automobile, a motor scooter, and XXXX bank accounts in XXXX. My reputation is important, although apparently not to the nice folks at Citi Bank. 
Ive tried everything else, perhaps your agency can wake these people up. 
I have since received a new card with a new number XXXX