Doesn’t this have more to do with the hardware bands available in the device rather than the carrier software installed on the phone? Perhaps as part of the race to the bottom on price Xiaomi forgoes hardware components that allow a given phone to operate on bands that are common outside the region it was sold in or the carrier it partners with. It would make sense if that was the case, because the people spending $20 USD on a phone typically aren’t going to be traveling a lot anyway

> plus two different India phones because of course West Bengal has to be different.

This makes no sense whatsoever. West Bengal has the same carriers and bands as the rest of the country.

> This makes no sense whatsoever

Neither does a 1:5 scale model of Big Ben, but Kolkata has that too.

I'm sure there's a knob I can tweak somewhere that makes it work, but a Xiaomi handset is like $20 so I never bothered.