Bogey, I don't know for sure, but unless you signed a six month contract at a specific price, I think they can do whatever they want.
Cable TV/internet services do the same thing. You notice a lot the ads show highspeed internet for like $25 for the first six months. They don't tell you that after that, they'll charge you twice as much. And if, like my area, there is only cable/internet service available at this time, they can do whatever they want.
Anyway, good luck. Hopefully they'll tell you that you can pay the price you agreed to for the remainder of the six month period.
TIS
"Mankind must put an end to war before war puts an end to mankind. War will exist until that distant day when the conscientious objector enjoys the same reputation and prestige that the warrior does today." JFK
And if, like my area, there is only cable/internet service available at this time, they can do whatever they want. 
