Emergency
With Automatic Crash Response, the built-in system can automatically connect to help in a crash even if you cannot ask for it.
Push 
to connect to an Emergency Advisor. GPS technology is used to identify the vehicle location and can provide critical information to emergency personnel. The Advisor is also trained to offer critical assistance in emergency situations.
See also:
Customer Assistance for Text Telephone (TTY) Users (U.S. and Canada)
To assist customers who are deaf, hard of hearing, or speech impaired and who use Text Telephones (TTYs), GMC has TTY equipment available at its Customer Assistance Center. Any TTY user can communicat ...
Transferring Service
Push to request account transfer
eligibility information. The Advisor can assist in canceling or removing account
information. If OnStar receives information that vehicle ownership has changed,
...
Format
Radios that have the capability of playing MP3s can play.mp3 or .wma files that were recorded onto a CD-R or CD-RW disc. The files can be recorded with the following fixed bit rates: 32 kbps, 40 kbps, ...