As I've said many times, I manage a live voip system. I have had calls and emails today about certain things not working (calls to a conferencing system not working and calls with users having issues with voicemail not being sent via email). Do you know what I did? I immediately called into the conferencing system and called and left myself a vm to verify I get the email. Since he supports a live system (based on testimony), if he got a message saying something wasn't working with voicemail, it would make sense for him to call and leave himself a voicemail. Do you know what I say when I leave a test voicemail for myself? I say "test" or "this is a test" or "okay test".
Outside of that what other purpose would he have for doing these seemingly work related calls?