Is it my fault?

I have lots of friends whom I am not really close to as they are mostly friends who just passed by my life (mostly those that I know of accidentally). Therefore, I do not see the point of calling them up (they are all guys) but not all are like that. Below are the existing cases:

Case 1:
This guy call me up (a malay)and said that I called him first, in which I did not. At that time, I was in a hurry and thus, cut his line; however, later on,I realize that perhaps he is from modern theater, a co-curriculum that I joined in university this semestre. I did not have their numbers and they have. So I messaged him back, asking whether he is from that activity. He missed called me, and well, since I have a code of miss calling with Yen Cheng, a friend of mine, I thought that was a sign that yes, he is from that thing. So I sent him another message again asking about the assistence that I might carry out for him. That was when he called again, now stating that he wants to get to know me better. Well, I am not a bias person and so am okay with it. We chatted for awhile and that was it. But he keeps miss calling me and when I messaged him, he did not say anything. What does this means?

Case 2:
This is a case with an evergreen (a nickname). But I hold no grudges against him. He called and said some mushy things and showed his frustrations upon my stalling for time or space. I have no idea, but it just felt weird...

Case 3:
This is with a friend whom I knew from the railway station. He is nice and would call me up when he has a lot of credit... However, I never called him up ever

Case 4:
This is with Tze Kang. He is very nice too. He would called occasionally, but we message each other quite frequently.

I never called any of them. Tze Kang is very understanding as he knows that I am a student still. I guess that goes the same with Hermie. I understand the reason evergreen was mad at me. But the rest? Is it my fault? As in I have to reciprocate their calls as well? Can it not be in message forms? Among all these men, only Sham seemed to be troubled by that fact. But, that is who I am. Even if I have enough credit, I would not call if I do not see the point in doing so. But, now I am feeling a tinge of guilt because of Sham... Hmmmm... Is it really my fault?