You can open a support case against the billing team, billing team will contact you in order yo clarify the month statement, if they made a mistake they can take actions.
You don't need a role based support.
All Google Cloud accounts get free billing and payments support.
For Billing Administrators
For Cloud Billing accounts you own, follow this link to contact Cloud Billing Support. Note that you must be a billing administrator on at least one Cloud Billing account to use this contact method.
Contact Cloud Billing Support
If you receive an error message when you attempt to contact Cloud Billing Support, consider the following options:
-Sign into a billing administrator account or ask a billing administrator on the Cloud Billing account to contact support on your behalf.
-If you use Google Cloud through a reseller or other Google Partner, you must contact them for billing support.
Alternative options to contact support
If you are not a billing administrator on at least one Cloud Billing account, and you don't know how to contact your billing administrator, visit our contact troubleshooter to find an alternative contact option, depending on your issue.
Support Contact Troubleshooter