not debiting my account

For the past 2 months Vodacom is just ****ing me off, my requested debit date is on 20th of every month and they have not been debiting on time. Called the call centre and they advised that it's there system problem, so I said cool pls debit my account for my statement amount, they go and double debitmy account and didn't even apologise nor credit me unpaid honouring chargers. This month I encountered same thing debit did not go through and today is already the 03rd Nov. Now I received a call to say my account is in arrears. Pathetic Service!!!!