I know that everyone's usage is different...but hope I can still get some input... Haven't had a data plan yet for any smartphone....just have a dumb cellphone....would like to know what is the real monthly total cost that you get billed for for minimal use of an iPhone...in other words should I expect with monthly service charge, taxes, fees, etc, about $75 per month or ?? Or if easier what is the range I should expect to see monthly? Currently, on AT&T in SF Bay Area, but can switch to other carrier if I want... Thanks for any all input!