When a contact has multiple phone numbers stored on
HTC One X+
, you’ll see the particular phone number used below the contact's name.
Keep in mind that your response will be sent to the phone number of the latest message you’ve received from this contact.
Messages screen, tap a contact (or phone number) to display the exchange of messages with that contact.
Tap , and then select another phone number of this contact.
Tap the box that says
Add text, then enter your reply message.