BEWARE- CONTRACTS WITH VODACOM ARE DANGEROUS

I have signed a 24 month contract with Vodacom on 18 August 2017. Just a few months later, from May 2018, they increased the monthly charges by nearly 17%. It is not fair. What is the use of choosing and signing a contract which you find affordable within a tight pensioner's budget? Vodacom misuse it's "big business" attitude to bully the consumer into something that is unjustified and totally unfair. Whether you phone them or write several emails, the answer stays the same, namely 5.8 of the Terms and Conditions !! Their reasons for applying clause 5.8 are very vague and irrelevant to the situation. I hope this will bite them soon.