Vodacom is want to bill me more what I signed up for

I signed up a 24 months contract with Vodacom in July 2017, which includes a vodacom smart tab and 1GB of data monthly for R129.00 per month. Firstly the blocked my accout and send it to their legal department without notifying me. And send me a number to call. They are ordering me to pay more than R5000 and I asked them for an itemized invoice and my original contract agreement and they havent sent it to me. I called and they are taking me from one department to another, some of their agents are rude shouting at me and ordering me to pay the money. They are telling me about some staff I dont know and they dont want to hear anything from me what they want if for me to pay me the money. I called them and I was on the call for about 2 hour being transaferred from one department to another . Please help me to resolve this problem with Vodacom, your help will be much appreciated as I am scared they might blacklist me .

Regards, Caroline ********** 570