Incorect bill and dented my Credit record

Vodacom has billed me an incorrect amount for the month of march. what is funny is that, They claim that i have used data more than 20Gibs and they forced me to pay for an itemized bill. My bill reflects that i have used 3.5 gigs on the month of march and the lady i was speaking to said i am actually paying for data i have no used. if the data is reoccurring and will be billed month to month then why has it not being debited into my account on the month of april. Vodacom has sent me a bill worth R900 + where as they have another bill that proves otherwise. what they are doing to my account is *****. My credited record has been dented by this situation and i found out that i cannot apply for personal things due to vodacom

I need Vodacom to clear my name on the NCR and correct the invoice they have sent me. I was buying data using my airtime and there is no way i could be paying R900+ for 3.5 Gigs