I'm only just old enough for it, but before mobile phones (I mean, they existed, but we were schoolchildren not businesspeople, before small relatively cheap Nokias I suppose) we'd 'call on' people to see if they were in and if so did they want to do whatever/go wherever... Thinking about it now, I think mobiles probably had quite a role in changing that: we got phones and then just started texting (hey wuu2 do u wnt 2 go in2 town l8r) instead.

I imagine now it's just straight to the latter, (albeit with less txt spk and more memes & emoji) because children get phones and start making their own plans at about the same age. (And not by coincidence probably - they're arranging to meet friends and going out alone, so parent wants to be able to contact them, to stay in the loop, etc.)