Petra: Hi Zack, I see you called. Sorry I can't pick up. In lectures all day.
Zack: Ok, when will the break be I can try then.
Petra: I will call you back in the lunch break because I am not sure if this lecturer will stick closely to the break times in the programme.
Zack: OK. 
Petra: Or you can write to me what it's about. I can type  and read I just can't listen or talk.
Zack called Petra, but she didn't answer because is in lectures all day. Petra will call Zack back during the break. Zack can write to Petra because she can read and write during the lecture. Petra can't talk or listen during the lecture. 