They have multiple plans to choose from. All internet is free, so you just pay for for the number of minutes you expect to use and the number of SMS messages you're likely to send. I have yet to put a dent in my minutes or, though I SMS alot, and the bill is between 60 and 70 a month, which isn't expensive from my perspective.
I think the phone is endlessly entertaining and great for roaming about the City, commuter train rides, or trips on the subway. So, I'm very pleased with my purchase.