Our Basic and Premium Plans come with a "starter pack" of minutes each month (500 minutes included for Basic and 2000 minutes included for Premium). Once you exceed those starter pack minutes, you'll be charged $0.05 for each additional minute you use.
So when am I charged for the extra minutes?
Those minutes are then calculated at the end of the month and charged on your next billing period. So if you used extra minutes in June, you would be charged for those minutes in your July to August billing cycle.
In order to set billing overage alerts ($1.00 minimum) you can view this article.