어디서 중요한 전화 올 데가 있어?
= Do you have somewhere to call from?
= Is there any phone call that you are waiting?
데 means "place,point,thing,matter,part,aim"
ㄹ 데 means "somewhere to do something"
갈 데가 있어? = Do you have somewhere to go? = Is there any place that you are supposed to go?