As you can see, the only two required features are the recipient's name and the message. The sender's name is optional but recommended, especially if your character's number is not listed in the directory, just to help the other player respond and give them more roleplay options. The Timestamp is optional, and really mostly gives a feeling of immersion and also helps me at the end of the month.
[Edit by Xeeyon] Cabal Phone Directory: click here to view
Reminders
The texts are In-Character. Do not text anything you do not want other players to know. Your character does not know what has been texted to another character unless you have been told or you could observe the same effect somehow (i.e., Izumi's floor getting sucked into a portal had an observable effect).
[Edit by Xeeyon]: Remember that the only character you control is your own. Before determining that another character has done/said something, please have the courtesy of making an agreement with the player about this first. Thank you!
Have fun!