Can I add / remove contacts from a group text message?
Sending group text messages or iMessages is a convenient way to have a conversation with multiple contacts using iOS. Going back to a message thread will resume this conversation with the same people. So is it possible to add or remove one contact from the list of people already on the group text?
The answer is no. Currently iOS (7.0.4) does not have the ability to add or remove a contact to an existing group iMessage or text thread. In order to modify the list of contacts in the group message, a new message must be created with the correct contact list.
UPDATE: iOS 8 brings this some of this capability to the Messages app. To add a contact to an existing group text message follow these steps in Messages:
1. Open the group message thread
2. Tap Details in the upper right corner
3. Tap Add Contact to add another party to the group message
UPDATE 2: You can now delete a person who you added to a group message by going to the "Details" panel and swiping on their name. Learn more about adding and removing contacts with iOS 8 here.