Clicks
Interest charged on a paid up account

I got a statement on 8th January with an outstanding amount of R12, 658.37. I paid all the outstanding amount on 23/01/2013. The new statement that I received on the 4th of February has an interest charge of R106.40, I only owe R15 on this account which was a purchase on 16 January 2013. Can somebody explain to me the logic in this R106.40 charge? This is daylight!!!