Establish relationship between two text fields
Both content types have to share a field, in the same way a both the database tables used in a INNER JOIN have to share a common field for the join to work. 

In Drupal, this is easy as you can reuse fields between your content types and in this wway joining the content types will be super simple with Views.

Current setup:


  Recording: field_called_phone, field_caller_phone
  
  Twilio: field_phone_number


Suggested setup:


  Recording: field_called_phone, field_phone_number
  
  Twilio: field_phone_number