For accounts created before September 18, 2021, you can update your contact information in the Security Settings screen of your personal my Social Security account. If you no longer have access to your cell phone number, you may request a reset code online.
For all accounts created after September 18, 2021, you need to sign in to either login.gov or ID.me, depending on which was used to create your account, to update your contact information.
If you choose not to supply a phone number or email, you will not be able to create an account.
For more information, go to the Security and Protection page.