Citibank Credit Card Complaint

Citibank Credit card department,

California

I paid off my CitiBank Visa in - or -. I do n't even have the card or a bill anymore to reference the account number! Today -/-/- i received a letter that I owe $120.00 + $22.00 in interest and $260.00 in fees with a total of $400.00. AND they are sndthe account to - - -. Which I believe is a collection agency. I want to know how all of the sudden I get this bill after at least -- years of this account being paid off. Please Advise I am afraid this is going i ruin my credit.