- First is restart your device if you haven't already done so.
- Reseat the SIM Card, i.e. Remove It and Reinsert it.
- Turn off Data, and turn it back on.
- Reconfigure the APN settings.
Things to remember, MMS go over data, so you must have your data connection active (even though the $25 plan doesn't include data). Group text messages, (and in some phones larger text messages) are considered MMS and go over DATA.