Why does my brothers phone calls me instead of the person that he was actually calling?

My older senior brother in another Province has an old cellphone and it had been working well until recently when he calls a person in a different Province across the country,I get called as well? Sometimes he is surprised that he got me instead of his friend that he knows for certain that he called that correct number?
What does he need to do in his settings on his phone to correct this problem?
P.S. He is not familiar with technology in regards to cellphone problems. Help ! He called at 4 Am and woke me up too in error.