Debit order dispute

I called vodacom in march this year to change my debit order and it was not done...i get paid on the last day of the month and till today my debit order still hasnt been changed! Last month they debited me and the bedit order did not go off obviously because there was no money in my account. I tried paying my bill through the app and its just as useless as them. I called today to change my debit order and i spoke to a guy named prince in the call centre he assured me that he changed it now and my debit order will go on the 1st of august with junes missed payment. Ok good. Not even an hour later they suspend my services because i missed one payment which was agreed apon to be paid on the 1st of august in full! Now its my problem since i cannot make immediate payment so i will still stay suspended till then! My contract expired in feb this year and im still paying them just so i have the airtime i dont need them...I want the person in charge to call me to sort this out its not my fault that my debit order wasnt changed the 1st time i called. I use my phone for business and im loosing income. I cannot except this its absolutely incompetance on there side.