I did quite a number of phone/Skype interviews during my search for a PhD position. For me, most questions centred on my academic background; my Bachelor's degree, my MSc with emphasis on my MSc thesis and most interviewers were keen to know exactly what experiments I had conducted (coming from Engineering background). I think interviewers wanted to know how my background closely matched with the PhD topic I was being interviewed for. As a prospective international student, one question which featured prominently was about my ability to cope in foreign land, if I were offered a place. I had no journal/conference paper on my CV and on certain times, I was asked why I had not published, so I assume those who've published some papers may be asked a question or two on their paper(s). My advice to you is to take it as an ordinary conversation, you must be relaxed, there's no reason to feel pressured or to panic. Since it's a phone interview, put down some critical notes, like your MSc/BSc thesis title etc. You never know, when adrenaline levels rise, you can even forget the name of your former university and the interviewer will be wondering if it's really you or you have hired someone to "attend" the interview on your behalf. Lol