1st--Well done you! If they want to talk to you--that's a GREAT sign.
2nd, I won't add anything to the prep ideas, as you have some great ones already, but don't forget that a willingness to address areas of weakness is a POSITIVE (as is an awareness of them). Trust me, you are NOT the only person applying for a Master's programme w/o SPSS experience and in fact, they probably have some sort of induction for that in place.
(On a side note, I also had to do a phone interview for my MA (Berkeley, Education). I did it in my pajamas in my dorm room in Minnesota, holding my best friend's puppy in my lap (I had borrowed her special for the day). I got in.
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Good luck!
