Hello...
You keep on saying that the problem lies with the carrier and not with Apple. But that is not true.
I am staying in India and using Airtel network. The nano-sim that Airtel provides supports 2G, 3G and 4G(LTE).
When I insert that sim, I get only the LTE toggle and when I keep it off, it switches to a 3G network when a very healthy 2G network is available. Since the 3G network is not strong enough, the battery drains very quickly. And sometimes when 3G signal is extremely weak, it switches to 2G. So it is not that your carrier blocks 2G altogether.
Apple iPhone by default takes the highest network toggle (in this case LTE). There should a separate 3G toggle as well so that people can switch to 2G even if 4G is available.
It is possible to do on Android devices but sadly not on Apple. You get either 2G/3G toggle(for carrier that supports upto 3G but no LTE) or 3G/LTE toggle (For carrier that supports upto LTE).
Apple should fix this issue.