Cancel Bkper Subscription on Google Cloud Marketplace
Go to the GCP Marketplace: https://console.cloud.google.com/marketplace/details/bkper-public/bkper
Scroll down to the pricing section
Click on MANAGE ORDERS
On the orders page look for the product Bkper.
Click on the three dots on the product line.
Select Change plan.
Choose the Bkper Free Plan.
Scroll to the end of the page.
Accept the additional terms.
Press the blue "CHANGE PLAN: button.
Confirm the change.
Your are now on the Bkper Free Plan, verify this in the books you own in the left bottom corner.