How to Permanently delete text messages from my iPhone 4S?

I have been reading and researching how to do this on all different help forums online and none are 100% working.

I've factory restored my iPhone and that helped kick out some texts but not all.

Documents and Data is turned OFF in my settings under iCloud.

I've deleted and synced to iTunes and that has not worked as well.

Is this an on going problem for people that have the iPhone?

Please any clarification would be appreciated!

Thanks in advance