Using the “Re-dial” Command
1. Press and hold 
for two seconds.
2. After the tone, say “Re-dial.” Once connected, the person called will be heard through the audio speakers.
See also:
Battery
The battery supplies power to start the engine and operate any additional electrical accessories.
• To avoid break-down or failure to start the vehicle, maintain a battery with full cranking power. ...
Ultrasonic Parking Assist
For vehicles with the Ultrasonic Rear Parking Assist (URPA) system, it assists
the driver with parking and avoiding objects while in R (Reverse). URPA operates
at speeds less than 8 km/h (5 mph), ...
Roadside Assistance Program
U.S.: 1-888-881-3302
TTY Users (U.S.): 1-888-889-2438
Canada: 1-800-268-6800
Mexico: 01-800-466-0801
As the owner of a new GMC, you are automatically enrolled in the Roadside Assistance program.
...