Disable 3G on devices that support 4G

I have an iPhone 5, with last update my carrier (vodafone) added the 4G button removing the possibility of disabling 3G

To use LTE i need to pay more so I have not a contract that include 4G network and the 4G button is completly useless for me

In my area the gsm receiption is not so good, so when I am at home with wifi, I used to disable 3G to force the phone using only gprs

Now I can't do it any more

I want to ask to apple if they can insert a triple button or something similar, to disable not only 4G but also 3G in iOS devices that support LTE networks

Thanks