Vodacom has the worst service!

I have been trying to get understand why Vodacom increased my from R237.00 a month to R499.00 per month. I have tried asking them why it has increased to more than double but no response on emails or calls. I had one call that I missed and that was it. My contract is 2 years old. I have asked them when this contract will cease as I want cancellation with immediate effect once it ceases. PLEASE HELP BECAUSE VODACOM HAS POOR POOR SERVICE!!!!!!!!!