From Zelda Legends Wiki
Grandpa Ulriria is a the only man of Koholint Island who owns a telephone. If you use any of the telephones in the telephone booths scattered througout the Island, you can talk to Ulriria, who gives you some advice on what to do next (though the advice isn't always so helpful). If you go to see him in Mabe Village, however, you will find that he is very shy in person, and can hardly convey a word to you. Incedentilly, if you use the telephone in Ulriria's house, you will call the only other person in Koholint who ever picks up: The Bucket Mouse.