Hi! If you call a number that it isn't on the folder or call an apartament with nobody at home the tone will be busy and keep like that until you press the go back button on the phone (you need to cancel the call manually) .
I'm experiencing the same issue. At least when I call a place where no one is home. The Go back button highlights but doesn't do anything if you click on it and you can't hang up the phone. You can return to the main menu, but that seems to end the game
