TLDR; never use google cloud systems for production.
Google cloud suspended all our projects due to the billing issue in their system they had.
Despite reassurances "your account will not be suspended" while communicating with billing support, all the projects were suspended at 1am on Saturday.
All the account payments were made and the billing cards are valid. There are no outstanding bills.
Never use GCP for production.
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Edit: full story by request, long read:
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Previous month billing didn't went through. Not sure if this was due to the billing outage google had (https://status.cloud.google.com/products/oLCqDYkE9NFWQVgctQTL/history) or financial transaction issue, however we went ahead and made a manual payment covering all the outstanding amount + extra. Despite the payment made, about a week+ later we suddenly started receiving threatening emails "Your Projects are at risk of suspension". Edited and updated the billing cards. Opened a billing support request clearly mentioning this is a production environment and all the bills are paid. They were "investigating" the issue and assured the project will not be suspended.
That way it's the bill-payers that notice and get in touch, not the poor tech on the out-of-hours rota.
Also, it only firewalled the customer's public IPs from the Internet - it didn't stop servers. That way when the account is settled there was often nothing for the techs to do.
Also it was only ever done after the bank reconciliation was marked as complete, just in case...
We relied on goodwill and recommendation of engineers for our growth, so were keen not to make their lives harder for someone else's bureaucratic (or cynical) mistake.