Citibank Credit Card Complaint

Citibank Credit card department,

APR or interest rate Massachusetts

My Citi Dividend credit card APR was raised from 9.99 % to 12.99 % after Citi had given me written notice to opt out of this increase. The increase was due to financial problems in the country. The notice stated since I accepted the increase by not opting out my APR would go to 12.99 % for only future balances. However it also stated that previous balances before opt out would continue at 9.99 % but Citi charged me 12.99 % APR for my whole entire balance, including the previous balance which was supposed to stay at 9.99 % as stated on notice. Basically over the years I paid 3 points more for past balances even though it should have stayed at 9.99 %. How do I go about addressing this discrepancy? Thank you very much for your time. - email : -