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Google Cloud Billing Support
I signed up for the Google Compute Engine and did not realise that I
would be charged $1000.
Google Cloud will automatically charge your card when you reach thresholds. The default for new accounts is $100.00 USD. Were you charged $100.00?
Additionally Google implements quotas for Compute resources. What type of resouce did you create that incurred $1,000.00 in charges? This would have exceeded your new account quota limit, so I wonder how you accomplished this ...
There is something odd about your first credit card charge being $1,000 USD as you should have received a number of charges for $100.00 each. After a credit card payment fails, you will receive billing payment notices. None of this would have happened mysteriously unless you do not read your email or SPAM filters blocked the notices.
Always take the time to learn what cloud resources cost. Understand that pricing, billing, resources and usage are important items not to be overlooked. Google, like most companies, is in the business to provide services and products that customers want and to make a profit while doing so.