Deleting a group text on an iPhone removes the conversation thread from your Messages app. This can be useful if you no longer want to receive messages from the group or if you want to start a new conversation with the same group of people.
To delete a group text on an iPhone, open the Messages app and tap on the group conversation that you want to delete. Then, tap on the “Details” button in the upper-right corner of the screen. On the Details screen, scroll down to the bottom and tap on the “Delete Conversation” button. A confirmation dialog will appear; tap on the “Delete” button to confirm that you want to delete the conversation.