Hi Neal,
First, restart your phone by holding the power button for 10 seconds. Make sure free calling apps like Viber, Tango or Skype isn't your default calling app or simply uninstall these free calling apps.
You should also check your call settings. Open the phone app -> tap on Menu -> tap on Call settings - > then scroll to the bottom and choose "Use Internet Calling" under Internet Call Settings. Make sure that "Only Internet Calls" is selected. I hope this will help you.