I can't contact her

I was a bit upset that I've been trying to call my younger sister already for the 5th times and still no response at all. I even sent her a message but still she ignored. So now I wonder what she is doing, either she's still at work or she's somewhere and didn't hear the ringtone of her mobile. Luckily before I explode for anger, she sms me and said sorry for not being able to answer my call. She was on the phone too but talking to our relative that will arrive tomorrow. It's his first time to be in our city, so she asked my sister's favor if its okay that she can pick him up. He is going to the city because he needs to buy a new milling machine. So I wish him luck and hope he can find the one that he needs for, I mean the one that his company ask to purchase.