contract increases

Hi<br> I got an sms stating that my smart l contract will be increased as of the 1st May 2015. Surely this is a breach of contract and surely no increases should be made within the 2 year contract period. I can understand the tariff charges but not the subscription. If this is the case I will put a stop order on all debits to Vodacom as I have 4 contracts with Vodacom amd this will be a substantial amount increased Per month. At no time was this explained to me that there will be an increase. If this is the case then Vodacom will get absolutely no business with me in the future. There are More than enough service providers out there that are more than willing to help out.