Shoving up Contract prices!!

Who gave Vodacom the right to increase per-existing contract tariffs!! Thats why we sign an agreement and a contract! its binding for the period! How can they now, after signing and agreeing on a fixed payment, increase that payment??<br> <br> Any contract now, which is bound by law, can now be altered just because. So, what is stopping Vodacom from doing it again!? Its a complete breach of trustt! You cant do this! So, 6 months down the line, Vodacom will just be \ Um