Skype is the most popular app for voice and video calling.In the mobile market, Skype has since long been dethroned by Whats App and Viber, but it still remains the most prominent tool for free communication on desktop computers.
Skype's video and audio calls are free within the network (i.e.
Unless you made a backup before you forgot your passcode, there isn't a way to save your device's data.
You'll need to erase your device, which deletes all of your data and settings.
Otherwise, oo Voo-to-oo Voo video and audio calls are free.
Use the service to call a Mac computer from a Windows computer, or an Android phone from an i OS phone.