To communicate with a base etc, by telephone.
I was too unwell to work yesterday so I called in sick.
To report; communicate (a message) by telephone or similar.
The hoaxer called in a bomb threat.
To pay a short visit.
I'll call in this afternoon to pick up my prescription.
To summon someone, especially for help or advice.
The government called in the army to deal with the riots.
To withdraw something from sale or circulation.