Unable to turn off the service

Can you identify which region is being billed?
Please confirm that active resources are terminated as described in the following document.
https://repost.aws/knowledge-center/check-for-active-resources

While your DB instances are stopped, you are charged for provisioned storage (including Provisioned IOPS). You're also charged for backup storage, including manual snapshots and automated backups within your specified retention window. However, you're not charged for DB instance hours. Remember that You can stop an instance for up to 7 days at a time. After 7 days, it will be automatically start up again.