It may be more difficult to call from a ship. Most members of the Army over there have internet access and a fairly good phone bank. Calls do tend to be expensive.
Of which they of course have access 24/7...
"Lieutenant, I'm going to take a little break from this firefight because I have to go find a phone. You see, sir (or ma'am) right now is the alloted time that the Supreme Spencer High Faculty will accept my call. Be back in a couple hours."