How to Undo a Sent iMessage on iPhone
The process for undoing a sent iMessage or text message on the iPhone is really easy and quick to do, but you have to be quick on your feet in order to do it properly, as it only takes a couple of seconds for an iMessage to officially send and get delivered.
To undo a message that you sent, simply swipe up from the bottom of the screen to bring up Control Center and quickly enable Airplane Mode. This will cut off all signals going to and from your iPhone, which will make it impossible for the message to send, and you’ll eventually get a “Not Delivered” message in red.
After you receive the red exclamation mark and “Not Delivered,” you can tap and hold down on the message and then select More. From there, hit the trash can icon to delete the message. You’ll want to make sure that you don’t skip this step, because once you disable Airplane Mode and your iPhone gets its signal back, it will attempt to send the message again.