Group text (in Messaging Settings) helps keep replies in one
thread while you're texting with a group of people. When it's turned on,
replies are sent as MMS (Multimedia Messaging Service) messages instead of SMS
(Short Message Service) text messages. To find this setting, in Messaging, tap
More 
>
Settings. This setting can vary by
mobile operator and might not appear. Your mobile operator might charge extra
for MMS messaging, and this service must be available with your current phone
plan.