You can send SMS text messages to cellphones and other Iridium phones!

Press Menu , scroll down to Messages and press Select
Press Select (Create message)
Type your message (using the number keys to select letters – max 160 characters) and press Options
Press Select (Send)
Press Add (New Recipient)
Press Select (Enter Number)
Enter the recipient’s number (including country code, for example a US cellphone would be: 1 ??? ??? ????, another Iridium phone would be: 8816 ???? ????)
Press OK, scroll down to highlight the number, and press Send