Can't say for GCP and Azure. But I run two small projects on AWS, with monthly billings of $8k and $150 respectively. I have always received very good support to any requests that I have made on both projects.

Nope. We had been testing in our development and staging environments for months. We were deploying to production the exact same stack and we got our quota revoked within about an hour. We must have tripped some random thing. We have absolutely no idea what I could have been though.