I hate calling adults... and I hate calling people to ask questions or to tell them that I won't be somewhere or something. I'm pretty fine with calling people my age.
There's a few exceptions. I'll feel bad like i'm interrupting something so my phone convos normally go like this;
Them; Hello?
Me; Hey. What's up/How are you?
Them; Nothing/Fine
Me; What are you doing
Them (answer 1); Sitting around. You?
Them (answer 2); Something busy
Me (answer 1); Bored, calling people to talk
Me (answer 2); Oh, nevermind then. Bye