They have a way for you to purchase time on WiFi...I believe the info is on their pamphlets in the back of the seat in front of you.
Check with the airline you are flying. You will either pay for browsing the internet or they will have a free network connection to watch their provided entertainment on your personal device. You can use bluetooth while in airplane mode as well as connect to their network for internet browsing. You can see what movies/shows they have available for your specific flight before hand incase you want to download your own.
If you fly Delta you get free messaging through Facebook messenger and two other thingz I didnt use so I forget <.<, when the plane takes off just connect to the plane wifi in airplane mode. If you want additional stuff like being able to brows the internet, you can purchase different plans. But it'd be cheaper to just take the free messaging and download stuff before the flight
Thanks! Your answer is awaiting moderation.