Hi there,
"Ring them up and do anything with" as in they could ring them up, and said friends would drop anything they're doing.
These discussions are always rather silly, because everyone has different ideas when it comes to classifying friends... but meh. The closest of friends are people you'd literally do anything for, but who'd do anything for you in return - now lots of people will think that describes some of their "close friendships", but I'd question whether or not that really is the case.
I'm sorry but you don't have 30-50 friends who you'd do anything for, and they wouldn't do anything for you... what you're describing are friends. Yes, you can spend a day with them and it won't be awkward... wow :| - would you be comfortable telling them all your deepest secrets? Would you be comfortable talking to them all about the things that ~affect~ you the most? If people say they have large numbers of "really close friends" there's either a difference in opinion when it comes to classifying what a "close friend" is... or they don't really have anyone they trust to a great enough extent to label them as such.
Myself? I'd say I have five really close friends, but I rather nice circle of "good" friends, as I'm actually quite easy to like (believe it or not!).