Iridium SMS service center number must be entered in the Iridium handset prior to sending text messages (SMS).
Usually, the number is preset at the factory, but sometimes you may need to reenter it using these instructions:
For 9555 & Extreme 9575 Phones:
In 'Menu' select 'Messages' - 'Settings' - 'Service Center'.
Enter 00881662900005 or +881662900005
For 9505A Phones:
Press the 'Envelope' key.
Scroll to 'Message Settings'. Press OK.
Scroll to 'Service Center'. Press OK.
Enter 00881662900005 or +881662900005. Press OK.
This must only be done once, the Service Center number will be stored in the phone.