which one is correct -i am at the office OR i am in the office?

Yes , both are interchangeable with slight difference. “At” : is used with buildings or non-specific locations. Ex…He is at home He is at work He is at the shop He is at the office. “In” : is more often used with specific rooms. Ex..She is in the kitchen He is in the meeting room.

Both are correct, depending on your meaning. “At” refers to a place, so if you mean you will be working at the office instead of working at your home, then use “at.” But if you mean you will be working in the office instead of working in the canteen downstairs, then use “in” to indicate the room you will be inside. You probably mean the first thing, so you should use “at.”

which one is correct -i am at the office OR i am in the office?

Both are correct, depending on your meaning. “At” refers to a place, so if you mean you will be working at the office instead of working at your home, then use “at.” But if you mean you will be working in the office instead of working in the canteen downstairs, then use “in” to indicate the room you will be inside.

You probably mean the first thing, so you should use “at.”