Billing issues not rectified - Debit order is more than what i owe

Vodacom opened up 2 x new contracts for but they cannot fix the billing and are over charging me for the first month... It is close to month end and I will debited more than what I owe Vodacom. I have been asked to call accounts for an issue that I can do nothing about, as a customer why should I have to follow up with accounts at Vodacom when they messed up billing. Please take this up with Lennon Samduth