Product: Credit card or prepaid card

I am filing a complaint against Costco-Citibank credit card company. The Citibank credit card company took over the Costco credit card contract from the American Express in XX/XX/XXXX. I did not personally apply for the Citibank card. My account was transferred from the American Express to the Citibank without being offered any other option by the Costco. In the later XX/XX/XXXX, when I did not receive monthly statement about the billing statement, I called the Citibank Customer services, its offshore agents in XXXX answered and told me that they are only responsible to collect the payments and do not have access to my account information to explain what are those charges for. I called several times again and eventually reached two Citibank agents in the US offices. Both claimed that they " can not even find the account '' or " can not even tell where the account is. '' In my 15 years of experience with the Costco-American Express and over 40 year experience with several dozens of credit companies, I have never had or even heard this kind of ridiculous responses from any credit card customer service agents! The Citibank suspended my account on XX/XX/XXXX, after only one month past due. The suspension of the Citibank Card had caused me enormous difficulty and inconvenience during the holiday seasons for shopping and vocations. The Citibank continued to refuse to provide detailed information on my billing statements. I called again several times without getting any help throughout the XX/XX/XXXX and XX/XX/XXXX. I also logged into my account online to search for information. Unfortunately, the Citibank online customer service website only provided the current monthly billing statement and the summary amount without any details for all previous months. While I am pursuing the information, the Citibank added late fees and high interest charges every months. In XX/XX/XXXX, I called again, this time the Citibank agent was able to find my account and able to tell me the itemized charges for XX/XX/XXXX-XX/XX/XXXX billing statement. But she said she has no access to the itemized charges for the XX/XX/XXXX-XX/XX/XXXXstatement ( Total amount id $ 1700+ ). She said she will research and send me the information when she found them. Nothing is forthcoming. In XX/XX/XXXX, the Citibank reported this past due to the three credit bureau and caused my credit score to drop from XXXX to below XXXX. My credit line increase request with another credit card company was denied. My application for new credit card was also denied. Now, a debt collector the XXXX XXXX XXXX XXXX claims that they bought my account from the Citibank and begins to harass me day and night by calling in the early mornings, late nights and on weekends. I am not aware if the Citibank has indeed sold my account to this company, and therefore release my financial liability with the Citibank. This debt collector does not use proper identify when they called. They offered me one settlement on the phone and then sent me a total different paper work in email and mails. Its modus operandi fits the warming we received from local police and DA office for fraudulent financial scheme. In my view, the Citibank 's Customer Service operates like a carefully crafted financial extortion schemes used typically by those loan sharks in the third world like XXXX, XXXX, XXXX etc. They deliberate delay in providing detailed information to the customer inquiries on billing statements. Then they can charge late fees and high interest rates to the account and demand for the payments for those fees and interests by threatening to harm your credit scores. For the entire period of my inquiries, the Citibank Customer Service never called me even once or returned my telephone calls even once. They have caused multiple financial harms, inconvenience and enormous emotional distress to me and my family. When I went to the Costco Customer Service in local store recently and asked for the separation of my Costco membership card from the Citibank credit card, their customer agent also confirmed that many similar complaints against the Citibank have been filed by the Costco customers. I am asking your agency to investigate and help me stop the telephone and mail harassment of this XXXX XXXX XXXX XXXX XXXX. Please urge the Citibank to resolve this issue in a professional manner without further harming me. Thank you for your attention to this complaint. I look forward to hearing from you soon. Sincerely,