I get calls all the time, but they dont usually say anything particular. Just like 'I saw a Bulbasaur, but I missed it!' Ocasionally someone will call and ask me to battle, but I never went back to any of em so far. Haha
Have a quick question for you. Is there any other way to make money in this game other than selling items/battling trainers? I have fought all the trainers in the game, so whatever money I have left is it.