nexus 4 owners -
How to set up the right APN on your Nexus 4
link -
http://www.androidcentral.com/how-setup-right-apn-your-nexus-4
Choosing the right APN
If you plan on using your newly unwrapped Nexus 4 on either AT&T or T-Mobile postpaid services, you won't need any extra configuration. The devices come out of the box with the carrier's proper APN settings preloaded in the software. That's a good thing, because you shouldn't have to fiddle with APN settings to use your phone right out of the box.
Our resident Brit, Alex Dobie, also explained that every unlocked phone that's come across his desk (that's a lot of phones) has had the correct APNs loaded or available without any special configuration -- even for the more obscure carriers out there. Maybe it's just lucky, or maybe he lives in a continent of civilized individuals that like network interoperability, who knows. What we do know is that using the Nexus 4 (or any other unlocked device, for that matter) on a Prepaid carrier here in the states takes just a touch more work.
We've gone to the major Prepaid carrier's support pages and found the APN settings that are suggested by the carrier. Setting up your device with these APNs should get you up and running without any major troubles. Fill in everything exactly as you see on the chart below, leaving blank anything either not listed or grayed out here: