Citibank "screws up"

I always pay my credit cards bill promptly at the end of every month before the due date. And i always sign on the bills after i pay them online via online banking through the Citibank website.

Couple of days ago, i received my bill and to my surprised my previous bill were not cleared and all my card had overdue interest and late charges. I called the bank and they told me that last month they had a glitch in their system and i even questioned them why i wasn't informed. They just told me that i just need to pay my bills without all those extra charges.

Yesterday i received 3 mailers informing me of the late payments again. So i decide to ignore them since they have explained to me over the phone.

This afternoon i receive a call from Citibank and this lady asked me when can i clear my overdue charges. I was so pissed off that i told them i will still make my payment at the end of the month as usual and they should stop calling me to chase me for payment since it was their system which failed. And all i get is "Please make your payment before the due date on the latest bill."

Seems like they are just keen on chasing payment from me even when their system failed on them. I wonder how the rest of the Citibank customers are being treated over this incident.