By that I mean how many phone calls make up a GB?
Phone calls do not generate gigabyte usage. Just about every major provider in the U.S. these days gives unlimited nationwide calling. There are some pay as you go type plans that have a limit on the number of minutes, not calls, you can talk.
As stated above, there are a lot of cell phone actions that generate GB usage, many of them unknown or unsuspected by the user. But if the actions are via a wi-fi network and not the phone company's cellular network, there should be no GB usage. There are some providers who offer plans that are exceptions to this last statement.
At one time an AT&T customer service person said I could stream 14 hours of music and consume "only" 2 GB. More recently, with the Internet down, streaming 3 hours of Netflix over the cellular network resulted in about 0.75 GB of data usage. Doing the same two activities over a wi-fi network, for me, would result in 0.00 GB of usage.
