Citibank Credit Card Complaint

Citibank Credit card department,

Unsolicited issuance of credit card New York

A visa account with citi was open via Costco without my authorization. Further when I attempted to cancel it over two consecutive months a charge was made without my authorization which I was told would be reversed. Over five months into the process, not only it was n't reversed but also interests has been accumulating. This neglect by citi visa will negatively effect my credit score ... Please assist me with the process of correcting it.