How do I remove obsolete numbers from iMessage

Hi DRR84,

Thanks for using the Apple Support Communities. I'm sorry to hear you are having these issues with Messages on your iPhone. If you are having issues messaging a specific contact, in this case because the updates to their contact info do not appear to be populating correctly, you may want to try deleting any of the current individual or group messages you have involving them, as outlined below:

If your messages aren't sending, or you aren't getting messages

Check your contact information:

1. Make sure that you're using the right phone number or email address for the contact.
2. Go to Settings > Messages > Blocked and make sure that the contact isn't on your block list.

If messages won't send to a certain person or you need help with group messages

Sometimes your messages won't send to a particular contact, or you might have issues with group messages. For example, you might reply to a group conversation and receive your own message. Or you might get a new phone number and see your old one listed as a recipient in an existing group conversation.

Delete the conversation* that has the issue and start a new conversation:

1. Open Messages and look at your list of conversations.
2. Swipe from right to left on the conversation you want to delete. Then tap Delete.
3. Open Messages, tap , and enter the phone number or email address of your contact or contacts.
4. Write a new message and tap send.

*When you delete a conversation, you won’t be able to recover it. If you want to save parts of conversations or their attachments, you can take screenshots. You can also touch and hold an attachment or message bubble, then tap More > Save.

If you can't send or receive messages on your iPhone, iPad, or iPod touch - Apple Support

Regards

I apologize, I should have been more clear in my explanation. While that cited section is referring to a slightly different issue (not able to send messages), the steps may still be applicable to your current issue (incorrect or old numbers populating in new messages, even after the Contact info has been changed). In some cases previous message conversations can cause this or similar issues, as noted in that section:

Sometimes your messages won't send to a particular contact, or you might have issues with group messages. For example, you might reply to a group conversation and receive your own message. Or you might get a new phone number and see your old one listed as a recipient in an existing group conversation.

If possible, try deleting any previous chat conversations that are still present, especially if they involved that contact's previous numbers, and then try restarting your iPhone and testing.

Regards