When I decided to sell my old iPhone, I wanted to make sure that all of my data and text messages were erased. I had a lot of private conversations, so I needed to learn how to permanently delete messages on iPhone. I used iTunes to back up my messages before deleting them so I could put them on my new device. I went into my Messages app and I deleted all of my conversations. I then went into my cached messages and removed all of those, so there was no way anyone could access my old messages.