This error often appears after jailbreaking and/or unlocking and it is mostly characterized by the fact that your iPhone can’t connect to the internet using the cellular data network, and you can’t send text messages anymore.
The first thing to do in that case is to reset the network settings and reboot your iPhone. If it still doesn’t work, then there is a more radical fix that will put everything back on track.
First, get on wifi and visit this website http://www.unlockit.co.nz/#_Custom from your iPhone. You should see this page, which will allow you to create a custom APN.
Under “Carrier”, tap the drop down menu and choose your carrier. Note that there are many carriers listed there and that it might take you a bit of scrolling down to get you where you want. So choose the right carrier and tap “Done”. This should populate the custom APN info.
Once the custom APN fields are populated, tap “Create Profile” and wait a bit. It will exit Safari, and take you to the settings application. Finally, just tap “Install” and this will set up your custom APN on your iPhone. Reboot your iPhone and you should now have Edge and 3G connectivity.