Both "I am out of town" and "I am out of station" are used to indicate that someone is currently not present in their usual or home location. However, the more common and widely used phrase is "I am out of town."
"I am out of station" is not as commonly used, and it might sound unusual or outdated to some English speakers. While both phrases convey a similar meaning, "I am out of town" is the more natural and preferred way to express this idea in contemporary English.