Join not using FK

Hi, I'm trying to make a join not using an FK. For instance:

If a have a Model Person, Phone and Call. A person has many phones.
There's no relationship between Call and Phone. Here are the model

Person: name
Phone: number, person_id
Call: number_called, call_date

I want to join Phone and Call by the phone number.

I'd like to do: <%= %>

How can I make this kind of join?