Very unhappy with yellodata!!

<p>I had a contract for R59 a month, every month they sent me an sms or when data is finished I switch back to regular data as . This month suddenly they bill me R293.63 for out of data. How is this even possible? I have had a new phone for the last month in which I haven't even used yellow data???? I cancelled imediately!! But this is steeling. I would like them to explain how suddenly they changed their way of providing data as out of data was never even mentioned when agreeing to the contract. also please prove that i even used the data.</p>