SMS texting is a cellular service, requiring the proximity of a cell tower that associates with your mobile service provider.
For texting over the internet, you would have to use some app that supports a different protocol. Apple uses iMessage (between Apple devices, with regular SMS as fallback for incompatible devices), WhatsApp uses WhatsApp messaging. Telegram, Signal, Kik, BiP, etc. are other options. Find some service that you and your peers are all willing to use. [Samsung phones have Android Messages, for online texting as well as cellular, but I believe the receiver would also need to have that same app for the online use.]
For WiFi Calling, many of these same apps can be used among various platforms. Also see: Talkatone, Google Duo, Skype, TextNow, Text Free. Some are US & Canada-only, but that may suffice for some users.