Can't get 4g

[Farhan Maitla]

I was using 4g when i was on 9.1.1. After the 9.2 update phone went into bootloop and I think i lost the modem so i installed the new version by fastbot method. But 4g wasn't available, i tried every but couldn't get it.. Tried 9.1.1 again, custom roms, different modems from 7.7 to 9.2..all the official firmwares even miui 8.5 but couldn't get 4g..Anyway to get it back?