Instead of trying to add fields or layouts, add more records displayed in a portal. Set up a relationship like this:
Contacts::ContactID = PhoneList::ContactID
Enable "Allow creation of records via this relationship" for PhoneList (double click the line between the two table occurrence boxes.)
Define fields as need in PhoneList such as a Type (for cell, home, fax, office, email...) and Number (for the phone number or email address).
Now place a portal to PhoneList on your Contacts layout and your user can add as many contact entries as they need by entering data in the bottom blank row of this portal.
Thanks this is great!