Hi, always...Welcome to PC!
I think a mature man, and a healthy partner, would realize your job is important and not throw a fit over your being in a conference when he calls! We all have to work, and you are obviously a conscientious employee! He should respect and value you for that instead of placing a guilt trip on you. The practical solution is for you to rid yourself of this immature man if he can't shape up and respect you for the professional you are. I know, I know!, this is rarely possible in a loving relationship, but what is loving about his behavior!
Patty