Dear student, 

Thank you for your repeated phone calling today. I could see your number on my caller ID and see that you called me every 5 minutes or so. I know I should have ignored the student in my office to pick up your call that was obviously so urgent and I apologize that I did not think to do that. 

Next time, please leave me a message letting me know what the urgent issue is and I promise I will call you back. Or better yet, when I see your phone number appear again on my caller ID I will automatically drop whatever I am doing to address your extremely urgent concern, the concern that was so urgent that you couldn't possibly leave a message.


Sincerely,
Me