I would look for a setting within the messenger app that says to use MMS for Group Messages. I use a 3rd party (ChompSMS .. same as Textra) and you can chose this option. This resolves the weird issue with group chats and iPhone users.
I was in Best Buy today and played with a G4. I couldn't find it in the MMS settings like the G3. I don't know which wireless version is was however.
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Interesting... May only be able to achieve it by going with a 3rd party one.