Why charge me late payment after paying

I have paid my account in full in May, i was behind with 2 months mind you when i paid they had already charged all the interest and what ever else. The balance was R 944.82 and I paid R 960.00. Made payment on 15 May 2019 then June I get a statement that am owing R97.85 for late payment, Interest and service fee.

Why am i being charged Late payment after making a payment??????????????????????????????????????????????????