Citibank Credit Card Complaint

Citibank Credit card department,

Payoff process California

Hello. Ihave had a Macys card for decades. Almost always I pay the card in full every bill. For the last year or so ... I receive the bill online. I log on IMMEDIATELY and pay in full. However, the nenxt month, without fail, I am billed anywhere from $1.00 to $5.00. I then have to call and ask what this is ... as I have paid the bill in full the same day it was received. I am told it is interest. I tell them I have paid the bill in full as per the E-ACT amount they billed. The rep has waived the interest lately but today I have another bill for $300.00, and it is the same thing. It is a holiday and I do n't want to have to deal with this again. This seems illegal and certainly unethical. I have every email and bill and payment saved for verification of the payments made. Can something be done about this? Why show an amount due on a bill ... it is paid well before it is even due and then there is some arbitrary balance? The Macys card seems to be through Citi. -