Citibank Credit Card Complaint

Citibank Credit card department,

Payoff process Texas

I called in to make a payment on my credit card and used the option to pay the entire balance due. This was on - - and my bill was due - -. I received a bill in the mail on - - saying that I owed interest of $2.00. How can i owe interest if I paid the entire balanxe due? When I called in they told me that the statement closing date and the due date were different and I was charged interest based on the statement closing date. They said it was my fault and when I asked if I would be charged interest again in - I was told yes.