If you are an iPhone 6 user on either T-Mobile or Sprint network, then you should be aware of the Wi-Fi calling feature. This particular tool basically allows you to make calls via a Wi-Fi network.
To use this feature, all you have to do is head to Settings and select the Phone option. There, you will find the Wi-Fi calls option. Tap on it and then you will have to turn on the Allow Wi-Fi calls.
Upon doing so, you will receive a confirmation prompt. Select Turn On and you will then be granted access to the feature.
When on an active Wi-Fi network, you can make calls to any number via the connection and this will allow you to save up on your bundled airtime. The Wi-Fi calling function basically makes communicating a lot more convenient and it is free of charge.