UNAUTHORISED AND NON DISCUSSED DEBIT ORDER

I received a debit this month of R2476-00 , this is R500-00 more than what my debit was of just under R2000-00 ! Firstly there was no notification sent to me of a increase , and furthermore how do you jump to R500-00 INCREASE!!! THIS IS SHOCKING and given the years with you as a client and this is a good solid years not just a couple, I will not accept this . Please ensure a manager calls me right away to resolve this matter amicably or clearly you rather lose clients