IPhone 5 little circle instead of 3G?

I just traded my iPhone 5 for another one because my previous one broke. Now this one it works perfectly but since I got it my service is bad. It almost always has a little circle next the sprint sign and when on my 3G it goes really really slow. On my previous phone I had never seen that circle only on this one. What can or should I do?

Turn it off and back on, something is wierd.

For the record the o is the symbol for GPRS (1G). Explains the speed.

Could be 2 things.
1. Check the APN settings in the Settings app.
2. The phone could be faulty.

The phone could be faulty. If you are in the same areas as you were with your previous phone, then the phone has a problem. First of all, check to make sure all of the settings are set up correctly. If you don't know, restore the phone to factory settings (making sure your info is backed up of course) and then re-install everything to your phone. Usually with Apple devices a simple restore will fix most problems. If you continue to face problems, I'd definitely bring the phone back to Apple as it sounds like there is a problem with it.