I am certain people have addressed the following issue before:

I know (or believe) that someone who uses broadband from a desktop or a laptop can make phone calls. If this is true, why doesn't the analogy graft onto cell phones that have broadband access? If it's possible, is it easier to get one of these phones, get a plan with low minutes but unlimited broadband access, and make all calls off the broadband? Do people do this?

See More: Using broadband in phones to call