James isn't in at the moment vs James isn't up at the moment

[Valerias]

English Grammar Tests, Elementary Level

ESL/EFL Test #102 "Phrasal verbs", question 1

I'm sorry, James isn't ......... at the moment. Can I take a message?

(a) in
(b) away
(c) up
(d) off

English Grammar Tests, Elementary Level

ESL/EFL Test #102 "Phrasal verbs", answer 1

I'm sorry, James isn't in at the moment. Can I take a message?

Correct answer: (a) in

Your answer was: incorrect
I'm sorry, James isn't up at the moment. Can I take a message?
_________________________

Hi!
Why James isn't in at the moment and no James isn't up at the moment?

Valerias

[Pamela]

Because "in" here denotes that he is not in accomodation

[Yankee]

Hi Valeria

I'm sorry, James isn't in at the moment.
This is a typical telephoning sentence that means "James isn't here". In other words, James isn't in the building (at home, in the office, etc), so it's not possible to talk to him.

I'm sorry, James isn't up at the moment.
Theortetically speaking, this sentence could also be correct, but the meaning would be very different!
It could mean that James is at home, but he's in bed (sleeping).

Amy

[Pamela]

But in general there is also an expession "up to the moment "denoting" to the very moment of ... speaking and etc.