Wrong number still showing in messages after port?

You don't need to turn off chat features completely but switching it off the back on normally solves the problem.

Android phones all differ slightly so the process might be slightly different depending on your phone

1. Go into the Messages app

2. Press the icon at the top right 

3. Select Message Settings

4. Select General

5. Select RCS Chats

6. Turn off the "Turn on RCS Chats" option then switch it back on. Wait a few moments and the number should update.

Another thing to check is the phone number linked to the SIM:

1. Go into the Messages app

2. Press the icon at the top right 

3. Select Message Settings

4. Choose your Smarty SIM (the name may be Smarty, Three, or something generic like SIM 1)

5. Near the bottom, correct the phone number if it is wrong.