Accumulating interest while paying ***

so i have an account in arrears with virgin active after my membership has closed. they put you on a month to month.

right i had a balance of 1390. been paying since april month 200 rand yet to pay this month so i call to found out outstanding balance cause to my mind it is R990 cause i paid april may and june. only to find out they are still adding interest and now my balance is R1192 something. now i ask my self how am i suppose to make lee way on this account when this is happening. its ****ing ridiculous. its enough covid has put us at pay cuts etc and now we still have this