Cliffhang

verb : to tell someone that you need to tell you something important on phone or text or IM, then hang up or go offline.

girl : hey , i needed to ask you something, its really important.....
boy: Go on, I am listening.

15 minutes later...

boy: are you there?
boy: did you just cliffhang me????
boy:hello

Spoiler: the girl fell asleep