If you've recently activated your phone and it's not yet able to make phone calls or use the Internet, performing a profile update on the device will force the phone to request its device configuration from the network which should get you up and running.
On your phone:
1. Connect to a WiFi network
2. Tap the phone app
3. Dial # # 873283 #
4. Tap Call
5. Starting Service Update message will appear - tap OK
6. If update is successful Service Update Complete message will appear after about a minute - tap OK
If update is not successful, the "Service Update Fails" message will appear. Make sure you are connected to a WiFi network and try again; if this happens again you may need to to run a factory reset.
If the update is successful but you only have voice/text services and not data, you may also need to try running a factory reset.