And in doing so it costs you nothing, to all intents and purposes. That's because WhatsApp is an internet messenger service app, that uses your smartphone's existing internet connection. So unless it busts your cellular data or home Wi-Fi data limits you can send as many messages as you like and it won't cost you a bean.
There are hidden costs though. By default WhatsApp saves to your phone any images or video that you are sent. This can lead to your phone storage filling up with images you never requested (my wife often sends me recipes via WhatsApp, making my iPhone a veritable cookbook). It also means you are downloading video and photo files, rather than viewing them over the web. In extreme cases this could mean you use more data.
How to stop WhatsApp Messenger saving photos to iPhone
Go to the Settings icon on the menu bar at the bottom. It looks like a small cogwheel.
Choose Chat Settings.
You'll see an option entitled 'Save Incoming Media'. By default this is set to 'On'.
Simply move the slider across to Off, and images and video will no longer be saved automatically.
They will, however, still appear in your personal Gallery, which can be viewed by other WhatsApp users.
In order to stop all WhatsApp media from appearing in your gallery, you need to create a .nomedia file or folder inside of your WhatsApp images, audio, and video folder. You can do this using a file explorer, or by hiding the folder in Quickpic.