How to Remove Content from Your iPhone
If you’re having problems with your iPhone and haven’t been able to fix them by turning the iPhone off and back on, you can try removing some or all of your data to see whether it’s the cause of your troubles.
To do so, you need to sync your iPhone and reconfigure it so that some or all of your files are removed from the phone:
Open iTunes on your computer.
Just like an iPod, you sync your iPhone by using iTunes.
If you suspect a particular data type is the culprit in your iPhone troubles, deselect that type of data in iTunes.
For example, maybe you suspect your photos because whenever you tap the Photos icon on the Home screen, your iPhone freezes.
If you have no suspicions, deselect every item on every tab in iTunes (Info, Apps, Music, Movies, Photos, and so on).
The problem could be contacts, calendar data, songs, photos, videos, or podcasts.
Plug your iPhone into your computer and sync it.
When you’re finished, your iPhone should have no data from the category (or categories) you deselected.
If that method fixed the problem, restore your data, one type at a time.
If the problem returns, you have to keep experimenting to determine which particular data type or file is causing the problem.