Wrong Invoice is debited from my account

Vodacom has allocated data into my account, the data will be sent on the 1st day of may 2018. I have been asking them to cancel it coz i did not agree to have that data. My contract with them is suppose to be R150 per month but they want to debit an amount of R900. i tried to cancel the contract and they keep saying they will call me back and the consultants dont want to transfer my call into the account department. the other consultant said will call me back yesterday but as ussual, they have empty promises. I cancelled the dibit order with my bank and should anything be deducted from my account from this day it will be *****. I need vodacom to cancel my contract and take their phone back