Bob Timmons wrote:
If you think this would be a useful feature, you might want to let Apple know.
Feedback - iPhone - Apple
(We are all users here on this user-to-user site.....just like you....and there is no assurance that Apple would ever see your comments here.)
I can't recall seeing many others who want to merge text message conversations. But it does make sense why you can't.
From a Google Search:
"There is no built-in functionality on most smartphones to merge text message conversations from different phone numbers, even if they belong to the same contact, because the messaging system treats each number as a separate communication channel. This limitation applies to both Android and iOS devices, where changing a contact's number does not automatically consolidate messages from the old and new numbers into a single conversation thread."