How to update email, phone_numeber in amplify auth using flutter?

Question

I am trying to update my email and mobile number as per their documentation below

https://docs.amplify.aws/lib/auth/user-attributes/q/platform/flutter/#fetch-the-current-users-attributes

but its throwing me an error like below:

user.phone_number: Required attribute cannot be deleted.

Is their documentation is wrong? or how can we do from the flutter app?

my use case is, once the user get signed In then they can update their email/mobile number by verifying the verification code.

Any help is appreciated, thanks