Vodacom non agreed payment changes

I got a call from Vodacom regarding my package and getting more data as my agreed on package was no longer valid as they explained. Next billing came and we paid more than agreed upon as well as our 2 year contract has been extended on to 3 years and a few months. I called Vodacom and was put on hold most of the 58 min call and i got the answer that they have voted and we need to keep on paying the non agreed amount as-well as an extra year longer or we can pay a penalty fee of 2000 rand. I would just like to have my normal amount to be paid on the contact. We have not agreed on any of these changes made as they only explained that the data plan would change and now the whole contract plan has been changed without any consent and signed documents?