An Internet telephony service provider (ITSP) offers digital telecommunications services based on Voice over Internet Protocol (VoIP) that are provisioned via the Internet.
Facebook messenger offers a VOIP service that uses wifi and cellular data only. Firstly you choose the friend you want to call in your friend list. then you choose either the telephone icon or video icon to start your call. If there is a green dot next to the telephone icon this means that your friend is online and ready to chat.
Then this screen will appear until your friend accepts the call. You have the option to put the conversation on speaker or mute the conversation. You can’t switch to video chat until the friend accept your call.
Once the friend accepts the call it will display a timer and you will be able to switch from video to audio. Once you have finished the conversation you can press the red button at the bottom of the screen which will end your conversation.
Once you’ve ended the call it will show you how long your conversation was and you will have the option to call that friend back again.
FaceTime is a feature on apple products which allows you to video chat with someone using wifi or cellular data.
When you chose one of your contacts it will give you the option to message, phone and FaceTime the recipient. The FaceTime icon is the video camera.
Once you select the FaceTime option it will bring up your camera and it will start to ring the recipient. You have the option to flip your camera so its facing you or flip the camera so its facing the other way.
Once the recipient accepts your call you will be able to see them clearly. you will also have a small box showing what your camera is showing them.
When you want to end the call tap the screen and click the red button to end the conversation.
The advantages of using Internet Telephony is that its free if you use wifi and cheap if your using it on your cellular data plan. However if your connection is weak when using wifi or cellular data then your phone call will become broken up and you may not be able to hear the recipient very well.