Bank Charges of R750.00

i have received R500.00 on my account now and when i checked Balance i am on -R222.00 i contacted *** Spoke to Pule he advised it because i have a debit of R29 X2 and R39.00 as well as R79.00 so all has been rejected so i owe FNB R722.00 for that i dint authorise any Debit order last month i was not Debited Pule put my call to ***** i spoke to Lucretia she advised they deal with Card ***** she transferred me to customer care i was on hold for an Hour, i have been up and down trying to DOWN GRADE FROM CHEQUE TO SAVING I HAVE BEEN TO THE BOULDERS BRANCH 3 TIMES BEING ASKED TO WRITE A LATTER FOR A DOWN GRADE FNB YOU MAKE ME SICK...