Billing alerts send you an email if your monthly spending exceeds an amount you specify.
By default, billing alerts are disabled. You can opt into receiving billing alerts on the Billing page of your account, in the Billing alerts section.
Check the box next to Send me an email …, enter the threshold amount in the Amount box (which is set to $20 by default), then click Save.
When your monthly spending exceeds the amount specified, you will receive an email at the email address associated with your account. You can change your email address on the Profile page.
To opt back out of billing alerts, uncheck the box next to Send me an email … and click Save.