Misleading price

I have been a client for the last 6 months with net nine nine thru evotel and signed up for the 75/75 mbps for R549pm, about a week ago I received a sms "Dear Customer, please note that your 6-month promo period has come to an end and your fee for your internet service has increased from R549 to R869. Ref: Evo-94743" but when I signed up nowhere it stated that its a promo for only 6 months, so I was misleaded, if I was told its a promo I would never have moved over to net nine nine as my ISP