Disappointed with Vodacom

I have been a customer of Vodacom for many years. Vodacom informed me that my 24 month contract (no phone) would expire in April but that it would continue on a month to month basis until cancelled. What they did not mention was that the monthly tariff would increase by 40% (R309 for April and then R433 for May). I was under the impression that cell phone tariffs were being reduced not increased. Is this a good way to retain customers????