From the Home screen, tap the Phone icon. (lower-left).> Navigate: Menu icon. (upper-right) > Settings. Then, tap the Wi-Fi Calling switch to turn on or off . If activating Wi-Fi Calling for the first time:
Hope that helps 🙂
Did you receive a new SIM by any chance when you upgraded your handset? Have you been able to try your SIM in another handset to see if you're still unable to receive texts that way?
Also, can you please confirm if you're having issues receiving calls or anything else?