Did You try to uncheck "use only 2G" in settings ?
In Bulgaria /vivatel/ 3G and 2G is working well with this device.
But, i have problem with GPS on my LY-F528.
I can turn it ON or OFF , but cannot catch any sattelites on clear space .
Google maps, IGO , GPS test , and other not working.
Where to find firmware update, or firmware mod for this device ?