Passengers can of course still purchase Wi-Fi on Southwest flights; the price is $8 for the duration of the flight for web browsing, email, and social media (but not video streaming).
At the moment, the free messaging is not available on all Southwest flights. If your flight does not offer the complimentary service, there is a charge of $2 per day, per device. Messaging on Southwest works with WhatsApp, Viber and iMessage, but not SMS messages. To see if free messaging is available on your flight, you can check Southwest's in-flight entertainment portal, according to CNBC.
Other airlines, like Delta, Alaska Airlines, and United also offer free messaging, though services vary across carriers. Free messaging is typically only available on flights with Wi-Fi, and may or may not include certain apps.
(Andrea Romano - Travel+Leisure)