I have friends who I am no longer living near because of moving for school and graduating from school.

I am wondering about communication. I feel like I have a connection to a couple of good friends, however, I am always the one who contact them. They never call me. Even when they say that it is great to talk to me and they sound really happy when we talk. But they never reach out. Should I just give up on these friendships as I am the only one that reaches out? And we aren't talking about me calling them all the time. It is maybe once every year or year and a half. They may say on facebook that they will call when I leave them a message, but they never call back. Should I just drop it?