Hope this helps:
GSM only:
adb shell sqlite3 /data/data/com.android.providers.settings/databases/settings.db "update global SET value=1 WHERE name='preferred_network_mode'" adb shell sqlite3 /data/data/com.android.providers.settings/databases/settings.db "select value FROM secure WHERE name='preferred_network_mode'" adb reboot
For LTE, change value = 11 For WCDMA, change value = 2
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