If you’re deleting multiple messages, this option will say something like Delete 5 Messages.

If you downloaded any media from the conversation to your Camera Roll, it will still be stored there.

If you have a conversation open, tap < in the top left corner of the screen to return to the Messages menu. You can also press on two message threads at the same time. When you do that, you’ll see circles pop up next to all of your message threads. [2] X Expert Source Josef StorziApple & Mobile Phone Repair Specialist Expert Interview. 7 December 2020.

You can also select all message threads quickly by holding down your finger on one of the blank circles and dragging your finger down in a straight line over the rest of the circles. All of the circles you swipe your finger down on will now be selected. [4] X Expert Source Josef StorziApple & Mobile Phone Repair Specialist Expert Interview. 7 December 2020.