Broken pay phones cannot make out going calls, but instead spout what seems to be nonsense gibberish when the phone is picked up. This is, in fact, a coded message which is essentially a recipe to cast certain spells. To learn a new ability, one has to locate one of these mythical pay phones, and decipher its message, but be warned, it will only tell you the correct way to do so once, repeat listening taints the incantation to backfire on the user.
Purple Monkey Dishwasher