can't switch to 3G

[wallstreet123456]

I have been using phone Info app from market and now I had a replacement phone sent to me because of some issues and when I install and try to use Phone Info App it turns off 4G but does not turn on 3G. I lose all internet/data connectivity.

I have tried to reboot and waited about 10 minutes hoping it would work but it does not.

Any idea what is happening?