Is there a way to turn off the 4g and use 3g instead? I'm thinking of trading in my thunderbolt for this phone but I wanted to make sure there was a way to do this first. I don't mind 4g, but I can't make it through a 12 hour day of work. With the Thunderbolt I had to turn the 3g off. I know the battery life is better on this phone though, so I could be wrong...