You are not a big customer to Google.
Let's assume that billions is actually 99B. So roughly 10B/yr. This is roughly 4% of their income in a year(~ 284B in 2022).
Big customers are at least double digit % of their income.
Google brought in around $284B in 2022, Big customers are at least double digits, so for Google, one needs to spend at least ~ 30B/yr to be considered a big customer to them.