VODACOM DOUBLE DEBITING MY ACCOUNT

Since the inception of my upgraded contract Vodacom has been debiting my account for two handset installments which is obviously incorrect. Ive called in numerous times and after many hours on the line with the call centre and despite promise after promise after promise to correct the problem of over charging which was acknowledged and i was given a credit note, i was being charged for both handset installment for the old and new contract. This month again Vodacom debits my account with R1200.00 which includes a second handset which is not supposed to be on my account. Ive tried getting through to the accounts department but every time i ask to be transferred the line goes dead( i'm quite sure its deliberate) the call centre agents are a means to frustrate customers as they are of no help whatsoever, this fight has been going on for months