How do I switch iMessages back to my phone number on a new iPhone?

Recently, i switched from my old phone, to my dad's phone (iphone 14 pro max), the phone was factory reset, yet for some reason the number still shows. but in my case the imessages is stuck on my email now (showing a different number) instead of my number, my whatsapp made a whole new account with the same number aswell. for some messages i still have imessages but others it only shows sms. Im absolutely confused on whats missing

[Re-Titled by Moderator]