No 3G while roaming with iOS 10 beta and iOS 10.1

[x.marX]

I have an iPhone 6 and out of curiosity, I updated to the iOS10 public beta and after that, phone is not connecting to 3G. It always shows Edge (E symbol) and the downloads are very very slow.
I contacted the carrier but they say its all OK from their end. They say that the connection requests from my phone is for 2G, not 3G. My phone is ignoring the 3G connectivity.
Then I deleted the beta software profile and updated to 10.1.
Same thing is happening with 10.1

I'm from India and my carrier is Idea Cellular.

One important thing to remember is that I'm Roaming (out of my native state) but yeah, I have turned on data while roaming option.

Any insight/solution into this problem is very much appreciated !!
Thank you !

Edit:
my "carrier" version is 25.5 by the way.
UPDATE:
I'm downloading iOS 10.0.1 to check if it would work.

 

[x.marX]

iOS 9.3.5 was working flawlessly

Now, I'm stuck in a foreign state which speaks a different language and when I'm on the road, asking people for directions, they seemed to make me more confused.
Google Maps is slow as a snail with 2G Edge data connection !!.
F***

 

[skyhawkmatthew]

This must be an issue with your carrier/SIM. I've been running iOS 10 since the first public beta, I use roaming a lot in multiple countries and I've still been getting 3G service.

 

[x.marX]

This must be an issue with your carrier/SIM. I've been running iOS 10 since the first public beta, I use roaming a lot in multiple countries and I've still been getting 3G service.

I thought the same !

But the carrier technical support guys are saying my phone is only requesting for 2G, not 3G.
They are saying the voice and data all being connected through 2G.

let me call them up again !