Say I received a credential from my government that says my post address is “xxx” and stored that in my wallet, and then my address has changed and this time I received a new credential from a utility company that says my post address is “yyy”, is there a way to overwrite the same credential by a different issuer?
Overwrite, no. However, what you can do is prove most of your attributes from the government credential, and then prove your mailing address from the utility company credential. You can show that the two credentials are both about you, and that the utility company’s credential issuance date is newer. This effectively overrides (but doesn’t overwrite) the address in the government credential.