[Nexus 4 Q&A, Help & Troubleshooting] sky0165:
If you send things to repair and they came back broken, you need to fix it by yourself.

I guess you're not used to do such things, so i'll make a quick tutorial for you, if you're interested of course.

1- Download [URL="http://www.purespeedx.net/index.php/Thread/160-KOT49H-PSX-PSK-v3-0-2-Pure-Speed-X-for-Nexus-4/?postID=3706#post3706"]PureSpeed[/URL] ROM, it's the best ROM you can find. Download the ROM, PSX Gapps and SuperSU in the PSX-Addons.
2- You'll need to download ADB to flash recovery. You can find it [URL="http://xdaforums.com/showthread.php?t=638150"]Here[/URL]. Extract it on the Desktop.
3- Install all Nexus 4 drivers. Connect an USB cable to your computer and wait all drivers to be loaded correctly. Switch from MTP to Camera to install both drivers as well. When it finishes, disconnect USB cable.
4- Once you have everything set up, open CMD (Windows + R button) and type CMD. A black screen will appear and you'll do the following: type cd: (location where you have extracted ADB folder. Ex: cd: C:\Users\zzz\Desktop\ADB
5- Connect your USB cable again and type: adb devices. If everything is fine, you should see a bunch of letters and numbers, like [URL="http://duarterenato.files.wordpress.com/2012/05/adb-devices.png"]this [/URL]
6- Restart your phone into bootloader. type: adb reboot bootloader. You should see [URL="http://cdn-static.cnet.co.uk/i/c/blg/cat/mobiles/nexus-4-root/fastboot1.jpg"]this [/URL]screen.
7- On ADB, type: fastboot oem unlock. You'll see an image like [URL="http://cdn.redmondpie.com/wp-content/uploads/2010/12/thumb_550_Nexus-S-oem-unlock.jpg"]this[/URL]. With this code, you'll unlock your nexus 4 bootloader to be able to install Custom ROM. Everything will be wiped, so be sure to backup everything and you can proceed.
8- Wait all the process, it won't take too long. Once you boot into Android, just type again: fastboot reboot bootloader.
9- This time we'll install a Custom Recovery. You can find it [URL="http://www.androidfilehost.com/?fid=23212708291678949"]here[/URL]. Download it and extract recovery.img into the ADB folder that is in your Desktop. Once this was done, type: fastboot flash recovery recovery.img. You should see some lines with OKAY.
10- Navitage using Vol + and Vol - and select Recovery option and press Power to enter it. You should see something like [URL="http://phota.me/AgsV.png"]this[/URL]. Tap Backup for future reasons, if you want to back to your stock carried ROM. Once complete, keep the backup somewhere safe and boot to android normally and transfer PureSpeed ROM, Gapps and SuperSu on the root of the storage. Once complete, type: adb reboot recovery.
11- Select Wipe and wipe eveything, except usb-otg. DON'T WIPE INTERNAL STORAGE.
12- Once complete, select Install and install PureSpeed ROM for first, when Gapps and for last SuperSu. I suggest you to wipe Data, Dalvik Cache and Cache for stability reasons.

If you follow this tutorial, you'll have one of the best ROMs available for Nexus 4 and also will be safed in case you want to back to your stock ROM.

If you still have problem using telephony, I suggest you to update your phone modem, but this is tutorial for another post.

I hope it helps you.