When you place a 911 call on a CDMA (Code Division Multiple Access) iPhone, the phone goes into emergency call mode once the call has ended. Emergency call mode blocks data features and text messaging to keep the line available for emergency services to call the phone back. Though emergency call mode ends automatically within a few minutes, users have the ability to manually disable this feature.
Tap the back button.
Press the "Sleep/Wake" button at the top of the phone or the "Home" button below the screen.
Dial a non-emergency phone number.