If you are using an iPhone in the United States or Canada, you can make free audio calls to avoid using all your mobile plan minutes. You need to be connected Wi-Fi and have the Facebook Messenger App. You can get that at the app store if you don’t all ready have it.
After you have downloaded the Facebook Messenger app on your iPhone, launch it from your iPhone Home Screen. To make a free call, enter the name of the person you want to call, tap on your friend when they show up in the search results and tap to send them a message. From that point, tap on the Info button on the top right of your screen and tap the Free Call button that will show up on the left about halfway down your screen.