Updating contact's info while keeping the same same text messages

How do I update my contact's phone number on a text conversation in an iPhone 6+? I update the phone number and the text conversation changes from the name to the old phone number. Meaning a whole new text conversation will begin for this contact. I don't want to have 2 separate text conversations with this contact. Is there a way to update my contact's phone number and keep text messages appearing in the same place?


Any help is appreciated.


Thanks