HTC One M9 - Manual (Page 139)

How do I add an extension number to a contact number?
While creating a new contact or editing a contact's details in Contacts, you can add an
extension number to their number so you can skip the voice prompts when calling.
1. After entering the number of the main line, do one of the following:
§ Tap P(,) to insert a pause before the phone dials the extension number. To insert
a longer pause, enter P(,) several times.
§ Tap W(;) to be prompted to confirm the extension number.
2. Enter the extension number.
Editing a contact’s information
Social network contacts cannot be edited.
1. From the Home screen, tap , and then find and tap Contacts.
2. On the Contacts tab, press and hold the contact, and then tap Edit contact.
3. Enter the new information.
4. Tap .
139 Contacts