How do I remove my phone number from old iphone that I want to use as ipod with other apple ID
I switched iphones and want to let my daughter use my 6plus as ipod with her own apple ID. So far all is set up but I can't activate iMessage and Facetime, though I've tried switching it off and rebooting and I saw that it lists my phone number still under settings/Phone. However I can't delete this phone number that should not me associated with this phone anymore from this old phone.
iPhone 6 Plus, iOS 12