I am surprised to see how the original poster was treated earlier. It is apparent from this many posts that it is a design problem with iOS 8 and not the carrier.
Sometimes Apple fails to understand their users' needs. In many countries, it is vital to switch between 2G/3G as and when necessary. Take my example, 3G often (mostly) gives a weak signal strength, heats up the phone and also drains the battery quickly. So I always keep it on 2G unless necessary.
What happens now is, even if I am not using Cellular Data, my calls are affected because of weaker network. Some people are suggesting changing packs, it is a good workaround. I am in middle of the road, I need 3G to quickly check out some navigation, at such time I cannot go on changing my data pack!
I am sure Apple is going to bring back this option in the next update. However, It would be even better if a patch is rolled out just for this. It is very important to me and other thousands of other users.