16.5% Increase in Subscription on contact less than a year old

I have been a loyal Vodacom customer for over 20 years. I have had my current contract for less than a year. I was very happy with the contract I took out and understood that it was a 2 year contract for R301.50 per month. I fully understand that there has been a vat increase however I have now received a 16.5% increase on my subscription. Vodacom you are conning people into taking contracts and then increasing the subscription less than a year after the contract is taken out. I was told you can legally do this ..... shame on you and no wonder you have a 2.2 out of 10 rating on hellopeter. Your company is ripping people off - absolutely appalling ..... you know you have us hooked in so now you will just milk us. This is beyond shocking. The call centre manager could not put me through to someone in higher authority and said someone would call me back - I gave them 20 minutes to call me back and surprise, surprise NO ONE BOTHERED. How do you justify 16.5% increase???????????????????