I believe the phone numbers must be stored to the phone memory in order to do that (at least that is how it is with my V555.) Then scroll through your phonebook to the number you want to set a Ringer ID to, and press the menu key. There should be something in there to set a ringtone to that number. Just keep in mind that the ringtone you set will also be the one you hear if that contact sends you a text message. And, as far as I know right now, there is no way to change that... Hope that helps.