Your Iridium's phone full international number is 8816XXXXXXXX.
From another Iridium or satellite phone, dial +8816XXXXXXXX or 00-8816XXXXXXXX
From US cell phones, dial 011-8816XXXXXXXX or +8816XXXXXXXX.
From a US land line, dial 011-8816XXXXXXXX.
From a land line in Europe, dial 00-8816XXXXXXXX.
Please be aware that calls to Iridium phones from landlines or cellular phones are very expensive (several dollars per minute), so please check the rates with your phone company before calling. You can use Two-Stage Dialing to avoid the high costs of calling to the Iridium phones.
Also, some phone companies may block calls to satellite phones by default, so you might need to unblock this feature by requesting it from your phone company.