Vodacom is ripping us off

Today I took an afternoon nap only to wake up to Vodacom having *****ed me over. I called the customer care, to find out why my airtime and data has disappeared, the lady told me my data got depleted and then the data charges ran from my airtime. So I ask her, why didn't I receive a notification to warn me about the data depletion, she tells me that it's my responsibility to keep checking my data. Okay then, so due to frustrations with Vodacom, I asked for the number to call to cancel this contract, and she tells me I will be charged 75% of the remaining contract balance. For what? I then proceeded to take an advance and bought myself 60mb power bundle, only for it to disappear as soon as I bought it. So what exactly am I paying Vodacom for because they just ripping me off ?.