How do I remove a phone number from an old phone.

Hi.

I recently upgraded my iphone (to Xs) and gave my old phone (iPhone 8) to my daughter. The advisor said I could just transfer my old SIM card into the new phone and give the new SIM card to my daughter on the old phone. This has mostly worked, except that my daughter is simultaneously receiving some messages and calls intended for me, despite having a new phone number of her own. How do I stop her phone (my old phone) having any association with my number?

Any help is greatly appreciated.