A is taking DC to a swimming lesson. On the way there, about 5 miles from home discovers they've forgotten the swimming kit. A phones B on the mobile to ask them to bring said swimming stuff to A's location. B doesn't hear the phone ringing because it's upstairs charging. A is now pissed off with B and blaming B for them being late to the swimming lesson.
So who is at fault really? A, B or DC (who is nearly 12)