What this means is that the phone is not correctly identifying itself to the network. Depending on the type of phone you have you can try by updating the data profile on the device. ON an android phone it will be main screen>menu>settings>about phone>system updates>update profile. ON the evo go to about phone prior to system updates. On most of our other device menu>settings> Data>update profile. This will have the device contact the network and refresh the information it used to connect.
Check out a fun infographic that teaches you how to increase storage, enhance security, improve battery life and clean your device.