I was about 13 I think. In high school. It was a Phillips with a little antenna, and I lived in the middle of nowhere so I didn't really have any signal at home - it was just for when I went out with friends. My first smartphone was an iPhone 4S and I was about 25 then I think.
I think I was 11 when my mum gave me her old nokia flip phone just so that I could text her to let her know I was ok, particularly when walking home from school and when I wasn't within her sight. Its all I really used it for, great little phone though!