Verify Minutes and Expiration
Push 
and say “minutes” then “verify” to check how many minutes remain and their expiration date.
See also:
Call Waiting
Call waiting must be supported on the cell phone and enabled by the wireless service carrier.
• Press to answer an incoming call when another call is active. The original call is placed on hold.
...
Ultrasonic Parking Assist
If available, the Ultrasonic Rear Parking Assist (URPA) system assists the driver with parking and avoiding objects while in R (Reverse). URPA operates at speeds less than 8 km/h (5 mph).
The sensors ...
Navigation
OnStar navigation requires the Directions and Connections service plan.
Push to receive directions or have them sent to the vehicle navigation screen. Destinations can also be forwarded to the vehic ...