Depending on your plan, usage above the included allowances may be billed:
The Usage tab shows the running numbers and an estimated amount for the current and previous month. Confirmed overage for a closed month is added to a following service invoice as separate line items.
Sometimes part of the current month is invoiced early. The Usage tab then also shows Billed so far (the amount already invoiced) and Not yet billed (the rest). Together they equal the estimated amount. A later invoice only includes the part not yet billed, so you never pay twice for the same usage.
If your bucket has a quota, you receive an automatic email when usage crosses 90%. At most one alert is sent per day; a new alert only arms again after usage drops below 85%. To avoid hitting the quota, delete data or upgrade your plan/quota from the Usage tab.
Cancelling the service deletes your bucket and all of its files. This is not recoverable.