I'm confused. So you're saying to change it to LTE...but then changed it back to Global? If that's the case, you didn't really change anything, so how would that fix it?
He's not on Verizon, but is on a network in Pakistan, so I doubt that will have any affect on most Turbo users.
For sure the most effective solution I've seen is to disable the G+ app. If that still doesn't fix it, there may be some corruption in the contacts storage, so I'd go into People, use menu to open the settings and find the export to storage command (just in case), then go into setting / apps, slide to "ALL" at the top, look for "Contacts storage" and tap it and then tap the button "clear data".
Again, this will erase all of your contacts from the phone. If you sync with Google or with Verizon Backup Assistant, they will all come back after the next sync. Otherwise you'll have to rebuild them, perhaps from the backup that you did in the above step.
But, like I said, I've had good luck with this since I logged out of my Google account. After the G+ app was updated a few weeks later, I updated the app, restarted the phone, and then logged back in. I've had no contacts crash since then when I receive phone calls.
This was a known issue with the G+ app on phones other than Motorola phones. They didn't list a changelog with the last update that mentioned fixes to contacts integration, but, again, it's fixed it for me.