I'm from Bulgaria (but this problem might not be Country related) and after update to iOS-8, I can't turn off my 3G or I have the option to turn on/off LTE only.
I don't want to be always on 3G because my battery consumption.
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I don't there is anything much you can do now since this is a change to iOS. After the update the toggle is only between 3G and LTE and no more 2G and 3G toggle. Also, you won't be able to revert to iOS 7 for long if at all, so try that if you really must revert this functionality.
From an experience standpoint, I really don't think you will run out of battery if you're on 3G. I would advise you to not use mobile data while travelling around a lot because with frequent changing of signal towers could lead to draining of battery.
Although I've seen a method to edit the preference file after jailbreak to fix this issue but it never worked for me.
I'm sympathetic to people in this situation since when the cellular radio is turned to max power to reach a distant cell tower, the battery drains several times more rapidly than if you were where coverage is good.
In the short term, here's things you can do to improve things:
Long term, unless the software goes into power savings mode more aggressively (or the function is still the same even though the label is different) - only a fix from Apple or your carrier building closer base stations will let your phone get longer battery life by reducing the power to the antenna.