I want to remove my current credit card from my account but it won't let me, because on Google cloud, I must have a payment method. I don't want to keep using the Google cloud platform. How can I remove Google cloud from my user account?
At GCP, billing account must have a valid payment method at all times. If you are unable to replace a failing payment method with a different, valid payment method, you can disable billing on your project.
However, when billing is disabled, your credit card information is retained on your account and GCP is unable to remove it. Credit card information is retained for reporting and auditing purposes only. Here is the documentation.
If you want remove your form of payment from potentially being used on other Google services, such as in your case Google Play Store, you can follow the steps for Deleting a payment method on Payments.