How to delete messages on an iPhone?

Ok so my friend has an iPhone with I message and he deleted all the messages but when he pulls up the Internet or tries to search something they pop up… Weird I know help how can he delete these messages? He has even turned off the app and turned it back on and they still show up how can you permanently delete messages from an iPhone? I have an iPod and never had this problem! Please give me lots of answers thanks!

Go into the conversation and click "Edit" then you can choose to either delete all the messages or only a couple. If you want to delete all conversations, or just a few conversations, go to all of youre messages and click "Edit" again. This will be on the top left side, where IN the message it would be on the top right. Do the same thing, and there ya go!