I finally got a new phone! It is a Sony Ericsson Z520a.
It has been a long time since I got a new cell phone, and it was getting a little embarassing. Most of my students had nicer phones than mine, and mine was starting to look more and more like one of those oversized phones from the 80's. (Which, when I was in the 80's, those phones didn't seem all that huge at the time.)