Citibank Credit Card Complaint

Citibank Credit card department,

Advertising and marketing California

I have a Home Depot Credit Card ( issued by Citibank ) and I had used it to purchase items on promotion ( 6 months no interest ) on -/-/2016. I was promised that no interest would be charged if I pay in full by due date - -/-/2106 ). I have paid the transaction amounts for each month in full since then. For the month of - the total transaction I had was $11.00 which I paid prior to the due date. However, Ciitibank is charging me a $25.00 fee since I did not pay the minimum payment of $25.00. I do not agree to the minimum amount that Citibank is asking to pay as it would mean that the 6 months no payment no interest is not what was promised to me.