Vodacom unwanted data

I renew my contract December 2017 and suddenly in May 2018 my subscription fee was increased R 40.87 per month excluding vat. I am on a Smart Top Up S contract, no I ********** -0. On my query first on 25 May 2018 @ 15h38, speaking to Lulama, I was told that according to my contract Vodacom can increase my subscription. I ask her that somebody with more authority must phone me to get more clarity on this matter. Hearing nothing by 12 June 2018 I again phoned at 12:16, speaking to Qaqambili, I was told that my monthly data allocation was increased trying to justify the increase. Nobody contact me to inform of the increase. I would also not agree to it as I am not even using all the data I am currently get.