***** conduct from ABSA BA Credit Card

I did not pay the full balance of my CC in month one. R1500+ interest charged to my card in month two. Fair enough. Cleared entire balance, two days before due date in month 2. ABSA saw fit to charge me R200+ on the statement for month 3, against zero owing. Queried this and received the bizarre response:

"If you omit to pay the full statement, balance interest will be charged over period of two months".

Really? Sounds decidedly ***** to me - interest charged when nothing outstanding?