If you find a charge on your Citibank credit card you want to dispute, the and can be handled online or over the phone with a Citibank representative. They'll likely issue you another account number in case your overall. Sign on to Citibank Online, go to “Service Center” and click “Card Block and Reissue” Provide the number of the card the disputed charge was made to. Provide your valid contact details such as mobile phone number and email address. Citi customer service representatives are available to answer your questions and Credit Cards. Citi Cards Have a question about how Citi is organized?