Why is this?
Best answer by Mohammed
Welcome to the iD Community!
Is this an iPhone by any chance?
The culprit for this would be iMessage.
What happens sometimes is when you've ported your number, iMessage doesn't update to the new number and needs to be done manually.
Can you try the following;
1) Try turning off iMessage (Settings > Messages)
2) then restart your phone (by pressing and holding the on/off button)
3) tap Settings > Phone > My Number and confirm that it is correct.
4) If it is not correct, please enter the correct number)
5) then turn iMessage back to On (Settings > Messages)
6) go to Settings > Messages > Send & Receive and see if the correct number is displayed under “Start new conversations from:"
This should fix the issue you're facing (if it's an iPhone you're using)
EDIT: Duplicate topics merged to clean up the community.