I sent an email to one of my prof from undergrad last week to ask for letter of recommendation for six graduate programs I am applying to. I took his class a year ago and I got an A from the course. I really love his classes and him as a professor back to college and we kept in touch although I graduated last year in May. I decided to go to grad school two months ago, which was already a bit late for Fall 2018 application because I am an international student and the deadline for us are generally earlier than for domestic students. Immediately after I made the decision, I invited this professor for a coffee chat and discussed my thoughts with him. He was quite supportive and recommended some excellent programs for me. I didn't specifically brought up the LoR thing during the coffee chat because I thought we were closed so it would not be a problem for him to say yes, and also because he wrote me two letters when I was in senior for my internship application.
I have all the materials ready now besides LoRs. I emailed him very politely last Friday to request the letters and he did not get back to me. I thought he did not check emails over weekends (although he did replied to me a couple times during weekends before I graduated) so I sent a short follow up yesterday. I know the school started on Monday so he must be really busy now. But the deadline of one school is coming in just two weeks so I cannot wait any longer and I am also afraid that I will annoy him if I keep sending emails.. I have his personal phone number, so should I call him? or approach to another professor? Please please help me.. Thank you!