Citibank Credit Card Complaint

Citibank Credit card department,

Billing disputes Tennessee

I took the Citi - - card due to an offer for credit off a flight I was booking. I made the payment for the full amount by phone, received a confirmation # and also a paper statement showing a balance of -. A few days later I started receiving calls from Citi saying my account was over due. I called back and they said the payment had been returned. I attemped to make the payment again and it seemed to go through again. Now a week later the account shows a balance again and another late fee and returned check fee.