Can’t change AppleID

I have a new iPhone 8, I changed to my email in iMessage and FaceTime, so I could setup my own AppleID (previously using my husbands AppleID/ email). It says I was successful setting up my AppleID, but when I go to settings and tap on AppleID, iCloud, iTunes and App Store it’s still showing my husband’s AppleID. I want it to show my AppleID but when I try to edit it says my email is unavailable. Please tell my how to fix this. Thanks