How to Delete iPhone Numbers
The iPhone lets you store multiple phone numbers for the same contact. A mobile number and iPhone number field are both available, eliminating the need to create multiple contact profiles for the same person in some cases. If an phone number becomes outdated or you only want to store the email and address of a person, you can delete the phone number associated with that contact.
Tap the "Contacts" app on your iPhone home screen.
Scroll down your contact list and locate the name of the contact you want to delete the phone number for. Tap on the contact's name one time to open a full profile for that contact.
Tap the blue "Edit" button in the top-right corner of the screen.
Tap on the red circle immediately to the left of a phone number. Select the red "Delete" icon that appears on the right side of the number.
Choose "Done" in the top-right corner of the screen to save the new profile.