that will depend on how long each call is - the longer the call the more data most likely.
why don't you try a quick call to someone and then go to your verizion account online and see how much data it used. if you cant see your acct online, you can call verizon at 611.
if you check before and after your quick call, you should be able to ezsily calculate how much data that call took and plan accordingly.
I have unlimited data on my android so i have NO idea what my data useage it or i could give you better advice.
I would like to ask a follow up question on the unlimited data plan Skype is used with: I am a resident of Australia and can't sign up for a service such as 'Verizon unlimited'. Are there any alternatives for an unlimited data plan, if someone lives outside US/Candada? Thanks for any hint.