dmcal is a private scheduling app for a small tabletop role-playing group. Players who choose to can receive text messages when a game session is scheduled, moved, or cancelled, and can reply to set their RSVP.
Texts are sent only to players who have signed in to dmcal with their Google account, entered their own mobile number on the My availability page, and ticked the box “Text me when sessions are scheduled or changed”. The form shows the notice “Message rates may apply. Reply STOP to opt out.” Nobody else can enter a number on a player's behalf.

dmcal: "Session 12" scheduled for Wed Sep 16, 7:00 PM EDT (Strahd). Reply Y = going, N = can't, M = maybe.dmcal: "Session 12" moved to Thu Sep 17, 8:00 PM EDT. Reply Y/N/M to update your RSVP.dmcal: "Session 12" on Wed Sep 16 is cancelled.Frequency: typically one to four messages a month, only when a session changes. No marketing.
Reply STOP to any message to stop receiving texts, or untick the box in dmcal. Reply HELP for help. Message and data rates may apply.