Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Did you actually purchase something, or you just want to make sure your credit card info is not in his account?
Launch web browser in incognito mode, go to https://account.live.com > sign in with your account, then check payment method, is the credit card listed there?
Then relaunch the browser in incognito mode, and have him sign into his account, and also check payment method. If your credit card is listed there it can be removed from there.