increase of installment on contract by sms

I have logged a complaint 31 March. I got an sms saying my contract monthly installment is going up. Vodacom rep**** they would contact me due course, up to now no one has bothered to call me. My contract states a fixed monthly rate for 24 months. I will take this to a attorney if I have to. This is false advertising to the public and not what my contract states per month for a fixed 24 months. My number is ***