I have the same phone. I had to do a hard reset. By doing this its like your phone is brand new straight out of the box. No mobile codes which pretty much leaves your phone open.
When you get a new phone, they mess with it first before you get it in your hands. They put in codes for their network so all will work properly. When I did the hard reset I couldnt send MMS nor recieve them either, but by downloading GO SMS, I looked at their settings and was able to get my phone right again.
If you can't get into the settings to do the factory reset or anything else, then this is the next best option:
- To do a hard reset turn your phone off.
- Turn it on again holding the power button and both volume keys at the same time until you see the Samsung flashing logo.
- Release all buttons and a little cute 3D android will show up. You then will have the option on what you want to do.
Remove your SIM and SD card, or they will be erased along with your phone.
Your phone will be brand new again.