Consider
I will call your office some time in the evening.
vs.
I will call at your office some time in the evening.
Which is correct — the version with 'at', or the version with no preposition?
Consider
I will call your office some time in the evening.
vs.
I will call at your office some time in the evening.
Which is correct — the version with 'at', or the version with no preposition?
They mean different things.
I will call your office ...
means you will use a telephone.
I will call at your office ...
means you will show up in person.