I've got a Windows Mobile 10 phone (Lumia 950). I've known that it is possible to do a Skype call, with or without video, between one WP phone and another, but I've never done it. Been thinking of trying it out. What I'd like to know is what are the impact upon the data plans, etc.? I'm sure it cost something, but is it an additional charge from Microsoft? Or is it free between 2 people both using WP phones? (Except for one's data charges, of course, from one's data carrier.) Is there some restriction, like maybe only 1 hour a month?