On XXXX/XXXX/15 we paid {$2700.00} thru the Citibank on-line customer service website for Citibank Master Card charges that were due. We were shown a balance of {$0.00}. 
Starting on XXXX/XXXX/15 thru XXXX/XXXX/15 we charged {$4900.00}. We had {$2100.00} in credits and payments, so our balance as of XXXX/XXXX/15 should be {$2800.00}. 
The Citibank on-line customer service website shows a balance that we owe {$3700.00}. 
When we called to inquire about the difference of {$960.00}, we were told by customer service and management that our payment on XXXX/XXXX/15 did not pay all our charges ( even though the balance showed as {$0.00} owed after the payment ) because the Citibank on-line customer service website is a different system than the statement system that Citibank uses to track your charges. 
We then asked why the Citibank on-line customer service website is available for our use as customers to see our charges and make payments if it is not accurately reflecting our Citibank MasterCard use. We were told by customer service and management that Citibank uses XXXX different systems. 
We have had this Citibank MasterCard for 11 years. We have been paying our balance in full thru the Citibank on-line customer service website for at least the last 8 years, and have never owed or paid any interest charges. 
We feel that Citibank has withheld posting some of our charges on the Citibank on-line customer service website so that we would not know the correct balance to pay ( or we would pay an inaccurate amount ) so then they could charge us interest on the unpaid balance the next month. The {$23.00} that we were charged for interest was minimal, but multiplied by XXXX of customers ( if Citibank is involved in fraud ) would profit Citibank XXXX of dollars. 
We would like an investigation. We do not believe that we owe the additional {$960.00} because the Citibank on-line customer service website showed a {$0.00} balance due after our payment of {$2700.00} on XXXX/XXXX/15. We used the Citibank on-line customer service website in good faith. If the Citibank online customer service website is not accurate and in sync with Citibank 's statement system, Citibank should not make it available for customers to use and trust. 
