I got invalid interest charges every month although I made full last statement 's balances by the due dates. I have been charges interest since XXXX to XXXX and I contacted customer service many times via email, messages, phones but Citi kept saying it 's valid charges and gave me no more explanation. I still make full payments except the invalid interest charges until the issue is resolved. Customer service specialists were not helpful and they always told me to do sth to avoid charges, but I followed and still be charges appr {$65.00} each month just for interest on zero balance. 
