If you are the one who pays the cell phone or internet bill in your household, then it is important to make sure that you use the data sparingly. You don’t want to use all of the data all at once especially if you are on a plan with limited data. If this is the case, you will need to monitor the amount of data that will be used when using certain apps. One of those apps is Facebook Messenger.
The amount of data used during a video call on Facebook Messenger would use more than only using a message. For instance, if you typed in your message instead of saying the same words over a video chat, then less data would be used. The length of the chat means more data is used. To check, look at your app data usage before and after the call.