Telkom prepaid became postpaid

I decided last year to go over to Telkom LTE prepaid after their adsl service became none existing. End of last month I decided to move over to another fibre service provider and downgraded my LTE to a R99 10G TLE and they said no issue it will be switched. End of the month my R999 goes of and when I called they said it was not prepaid but post paid. Looking at their invoice they reversed it on the invoice and changed me the new R99 but never did a real reverse on my bank account.