Two of my gae projects has been disabled billing but still gets charged.

[Tapir]

I have disabled billing for the two project at May 3rd.
But their quotas pages still show they are charged at May 4th and May 5th.
Is this a bug of GAE?

[George (Cloud Platform Support)]

After you close your billing account, we will bill you for the usage you accrued prior to cancelling your service. This bill will be the last bill you receive, unless you reactivate service. You may gather more detail from the "Create, Modify, or Close Your Billing Account" documentation page. You can solve billing-related issues based on the information provided on the "Resolve Billing Issues" page. 

[Tapir]

On Monday, May 7, 2018 at 4:32:13 PM UTC-4, George (Cloud Platform Support) wrote:

After you close your billing account, we will bill you for the usage you accrued prior to cancelling your service. This bill will be the last bill you receive, unless you reactivate service. You may gather more detail from the "Create, Modify, or Close Your Billing Account" documentation page. You can solve billing-related issues based on the information provided on the "Resolve Billing Issues" page. 

I didn't close my billing account. I just disable the billing from the setting page of my app engine projects.
In other words, I just set the "Daily spending limit" to zero.
Isn't this sufficient to avoid GAE scheduler create too many instances for my projects?

[George (Cloud Platform Support)]

The recommended way to disable billing can be found on the documentation page mentioned in my previous answer.  Under Projects linked to this billing account, locate the name of the project that you want to disable billing for, and then from the menu next to it, select Disable billing.