Data depletting within ten days.

On the first of August 2015 i upgrated my contract, where in the past before the upgrade i almost never used all my data per month, since the upgrade all my data is depleted befire the tent of the month. Vodoacom says they dont know the reason and they cant help me. I have to buy additional data every month,5 times more than my normal ussedge. If vodacom dont fix this i will stop my debit order and i will not pay a sent on this account untillmit is fixed.