The IRS's Child Tax Credit Update Portal allows you to to change the bank account where your child tax credit payment is deposited, or to stop monthly payments by unenrolling.
These actions apply to the individual only. If you are married and file jointly, you and your spouse must unenroll using the Child Tax Credit Update Portal. If only one of you unenrolls, you will still receive half the normal payment.
Similarly, if you are changing bank account information, both of you must make the update so both halves of your payment go to the new account.
See the Advance Child Tax Credit Payment FAQs for more details.