When i get a picture message i cant download it

Here are a couple of things you can try:
You need to see if your MultiMedia Messages (MMS) are set correctly.
1. Go to messages and click on Settings.
2. Scroll down to find Multimedia Message (MMS)
3. Set Auto Retrieve to OFF
If that doesn't work try this:
1. Go to Settings
2. Go to Mobile Network Settings
3. Click on Access Point Names (APN)
4. Tap on Menu - (lower left side of phone)
5. Click on Reset

Try both these things and that should fix your problem.
Good Luck