Are you using an iPhone perchance?
When you change SIM cards with an iPhone you'll encounter a common problem with the number not displayed correctly on calls and texts. If that happens just follow these steps and you'll be sorted
Go to Settings > Messages and turn off iMessage.
Then go to Settings > FaceTime and turn off FaceTime.
Now turn off your iPhone
Restart your iPhone by pressing the side button (or the button on top of the iPhone if you have an 4.7in iPhone).
Now go back to Settings > Messages and turn on iMessage.
And go to Settings > FaceTime and turn on FaceTime
iMessage, and your number, is now set up correctly
Hope this helps