At the very top of the message it will say "add to contacts" or something along those lines. Then you can either create a new contact with that number or in your case you would change it to a existing contact by tapping on that contact and changing the number.
At the very top of the message it will say "add to contacts" or something along those lines. Then you can either create a new contact with that number or in your case you would change it to a existing contact by tapping on that contact and changing the number.
If an SMS text message is rcvd from someone who is not in your contact list, there is no way to add that new number to the Contact list, as far as I can see. The only options at the top of the message are "edit" (which you can only clear all, delete or forward), and Messages (which takes you back to your messages list).
So in order to add the newly arrived number, you have to remember it, then go through the normal add a contact steps, outside of the text message application.
If there is a way to add a new number from the new text message, I would love to hear about it!