Anybody pick up the telephone, please~~~?

Suppose that one of my old friends - Guojun (I guess Robert might be his English name...well, I just guess from his Email) - must have finished from his military duty in Taiwan in the end of May, I tried to telephoned him today. We used to be working in the same laboratory when we're studying in graduate school, and we haven't contacted since my graduation, that is, more than 2.5 years. He's such a hard-working guy that I really admire him. He knows many techeniques; for instance, he taught me how to make a "paper-made micro spatula" and I still remember how convenient it was. We usually talk about our experiments and exchange experiences as well as results each other. Unfortunately, for some reasons he didn't have a good life during his grduate school days (neither did I though), and thus got stomach ulcer. Riiiiiiing~~~~ Riiiiiiiiiing~~~~... Nobody answers. I tried many times but it eventually comes out with either no-answer or engagement. I'm sure he hasn't moved as I just sent him card several months ago and he replied me. Mmm...It's odd. I'll try several days later.