Most schools allow phone-interviews. I thought I bombed my Darden phone-interview because I babbled for ~1hr with minimal interruptions from my interviewer. It was very difficult to manage a 2-way conversation.
I encourage everyone to choose either an on-campus or an alumni interview. AdCom will probably note your sincerity and eagerness to apply to the school. After that near-miss Darden application, I traveled to my neighbor countries for 3 different alumni interviews (got great results).