I call purely in order to arrange rides or to find out where people are hanging out.
Lately, though, I've been calling my mom because she moved to Arizona and she's all super mom-y and sentimental and stuff and wants to talk to me because she doesn't see me everyday. So I call her to talk.
I find phone conversations weird and stilted, so I'll only call someone if there's a particular reason; I want to invite them to something/find out what's going on/etc and they haven't replied to texts.
I call my husband / sister / mum / dad just to talk and catch up. Most other people I know I call only for a "Where are you? We're outside the theatre and can't see you" sort of thing - I'll catch up with them via email / facebook / in person rather than on the phone.