On iOS devices, carriers get much better controls over network settings as compared to what they get on Android devices. But it’s not helpful for users when a carrier decides to take critical functionality away from their phones.
I live in an area where network reception for my phone’s carrier is fairly weak. So I used to keep my phone’s network mode to 2G to keep the network bars filled up. However, I recently reset my iPhone, following which I received a carrier update on the device, not knowing what it might do, I installed it on my phone.
Now, I’ve lost the ability to switch to 2G network mode on my iPhone X. All I get now is an option to turn off 4G. Nothing else. And turning off 4G is the toggle to switch to 3G network mode on my iPhone now.
Before the carrier update, I had the option to select 2G, 3G or 4G under cellular data settings.
So, point is, if your carrier doesn’t want you to use 2G network on your iPhone, they can lock that option on your iPhone by simply pushing a carrier update to your phone.