Alarmed

I mean just set an alarm on you phone, I usually have multiple super annoying alarms to wake me up in the morning

My phone has failed me so perhaps it was the same for him? Perhaps for whatever reasons he doesn't have a phone or an alarm clock? Maybe someone else is sleeping in the same room and alarm would wake that person but sister is able to wake him only?
In any way if sister agreed to wake him but didn't it is not his fault.

That's wrong and petty. Smh...

Wake yourself up.

Don't tell him the one trick alarm clock companies hate!!

Sure you missed class but imagine if she woke you with say pots and pans banging and screaming 😱. Since you can't use an alarm.

I hate when people ask me to wake them. I always set alarms when I need to wake up

people really out here acting like it's OPs fault his sister didn't do him the favor she said she would.