ATT phone bill!!!!!!!!!!!!!!!!!!!!!!?

[DJHFDSADFLHADF]

for some reason my ATT phone bill came to 300 dollars this month! last month in March i bought a new Iphone 3GS, so could that be the reason?? our phone bill basically came 100 dollars more when i was told the data plan is only 30 dollars!

is this only for the first month??? or will i pay this much forever?!