I need to find out how to make sure that once I delete a message it is completely erased from my phone. I don’t want it saved to iTunes or anywhere else. How can I make sure of this?
if u want to do so restore it then set it up as a new iphone
As far as I know messages are still stored in some database on the iPhone after being deleted within the Messages app.
Therefor I think the only safe way to get rid of them is by restoring the iPhone and "setup as a new iPhone".
* Setup as a new iPhone is the crucial point here, otherwise data will be restored from a backup.
Once that it done you will also have to delete the backups created by iTunes of the device since they also contain messages.
Deleting a backup in iTunes.
If you are using iCloud for backups you will also have to delete them.
All in all this means you will have an empty iPhone with no data on it whatsoever. Contacts, Music, Apps and whatnot has to be synchronized again and/or setup manually. Things that were only present on the iPhone will be lost.
To permanently delete messages visit the link below -
How to Delete Emails Instead of Archiving Them -
First of all, iTunes isn't used for storing any data, so that's not a concern. The real concern is that for all practical purposes, you cannot securely delete the data on your iPhone, much less any smartphone. There are ways to do it, but since nobody knows whether Apple has implemented the a method properly, you can't rely on Resetting your iPhone to factory defaults.
There are a few iPhone apps that claim to do this, but they haven't been subjected to independent testing to verify their claims, so you can't rely on those, either.
If you want an idea of how complicated this is, take a look at this article: http://static.usenix.org/events/fast11/tech/full_papers/Wei.pdf