Hi @LivinginHope There are a few Methods. if you go to Samsung Account on mobile-Profile Information-Email-Change, a new one can be entered.
It can also be changed via the web via this link https://account.samsung.com/membership/intro once signed in go to Profile-Samsung Account Settings-email ID. once you click on the email it can be changed from there.
I do not work for Samsung or make Samsung Products but provide independent advice and valuable contributions.
My Device- S21 Ultra 5G ( SM-998B/DS ) CSC= BTU , 12GB/256GB
One Ui 5.0,Android 13 .
@LivinginHope Further to the great advice from James, you can give our Accounts Team a call on 0800 995 1079.