Like everyone else has been saying, they put that $2.00 charge on your card even after a balance of $0. I sent a message via their website, but excpect a robotic response and will be calling to cancel today before they tack on their "late fee" to their $2.00 scam charge.
No matter how tempting it might seem, don't. What they fail to tell you is you only get the opening discount up to $250.00. After that, nothing. Citibank are the ones that own/run the cards. I've caught them more than once with fees that were not even supposed to be on my account. They've corrected it everything but still. If and when I do use it, I scan the statement. Do not recommend.