Cellular data rates might apply. Like a group iMessage, every recipient can see each other and all replies are sent to every member of the group.
If Wi-Fi is unavailable, iMessages will be sent over cellular data. These messages are always encrypted and appear in blue text bubbles.
The only way to prevent this behavior is to disable iMessage altogether. Learn more about the difference between the message types. You can contact your mfssage to determine how large a group you can send to. Different providers impose different aending on how large an MMS group message can be; some providers' limits are as low as These messages are texts and photos that you send to other cell phones or another iPhone, iPad, or iPod touch.