Changing Contact Phone Information (Field modification)?

On a contact page there's a list of fields for phone numbers:

Business
Fax
Home
Mobile
Pager

How can I access this entity to change a field name?

  • I want to change the label "Business" to "Direct" because the business phone number is with the company.
  • I want to remove "Home" because no one gives out their home number or doesn't have one (and if they have a mobile it's quicker anyway).
  • I want to remove Pager because no one has a pager anymore.