Vodacom increase existing contracts' subscription!

I entered into a contract for my minor son for a fixed amount i.e. R79 pm. This month I received a letter that it is increasing to R110 due to Vodacom's expenses increasing. My son will receive R110 airtime now. I have no desire for the child to receive more airtime. If Vodacom is in such dire financial distress, why do you increase the amount of airtime? Leave the contract as is. Fixed is fixed!!!! It is shocking that a company can one sidedly decide to change a contract. I'm sure it is justified somewhere in the font 2 T&C's to cover your self. <br> This is not the way to look after existing customers. I WILL NOT!! renew this contract once it expires. <br> But I guess if you increase your new contract prices, you can't fool people into enterring into contracts, so just entice them with cheap contracts and once they signed, you increase the monthly cost. Values, Vodacom??? You surely know how to get customers backs up. <br> Don't even bother to contact me, the number provided below is a coy phone where, unfortunately, I don't have a choice of service provider. With the recent upgrade of this phone too, the service from Vodacom was just as pathetic. Vodacom don't care!