Originally Posted by JimmyStephans

This is easy to answer -

There are no cell phone towers in the ocean so no cell signals. No text messages, etc. Even onboard WiFi doesn't help because that is just signal from the device to the WiFi Router in the plane (a few feet). That router then needs to send by some onboard satellite transmitter system to modern digital satellites to ground to hit normal internet or phone systems.

Satellites that are modern, such as those used in the GPS on a phone or to carry digital data like Internet or TV, are not positioned down in that southern Indian Ocean because there is nothing there that calls for things like traffic directions, TV, etc.

Just a couple of mid-90s satellites cover that far south and they don't have the tech to do global positioning. They are just relays for messages from ships at sea and planes. Short messages, like text or email, that have nothing to do with positioning but more things like weather reports, condition of engines, things like that. The only time they are used for positioning is if the pilot types in a message, such as "We are one hour out of waypoint Harper22" (which never happened on this flight).