Phone dropped, lost 2g/3g. LTE works

So the title says it all. I dropped my phone, after which just get LTE,. If I toggle to 3g/2g, it says No Service. I replaced my simcard from tMobile, still no luck.

How do I know what has broken? Will flashing stock Radio only help? Do i need to take a backup of something before flashing radio?

I am currently running 4.4.4 stock with root and xPosed framework. Phone was purchased on its launch, so, its not under warranty anymore

Any help is appreciated.