Unauthorized changing of price plan on Data contract!

<p>Hi Vodacom,I have a really big problem with 1 of my Data contracts. The data contract in question was changed from a top up contract to an open line without my consent or any notification.This is really upsetting as this contract was taken for my brother and now I have a really big bill which I am not prepared to pay since this has never happened before because this was a top up contract to my knowledge so it's impossible to go over the 2 GB limit.Please assist me in this matter or I will have no choice but to cancel this contract immediately.</p> <p>The number in question is ********** 630.</p> <p>Regards</p>