My new mobile phone is plugged with an old SIM card, and the new mobile phone has SMS and call records of the old SIM card. What happened?

That's because your phone number was stored in the calling card before, so you changed your mobile phone without changing the card. Insert the old card into the new phone, and the phone will automatically read the number in your card and display it in the new phone. If you don't want to show it, just set it in the phone book. Thank you.