At AdStage, we bill in advance for both monthly and annual subscriptions. When you upgrade your plan manually, or an auto-upgrade occurs, our payment system finds the difference between the amount you've already paid for your initial subscription and the amount of time on your new upgraded subscription, and charges the prorated cost to the payment method on file.
For example, if you're on our Full Suite Pro plan ($1,328/month), and your ad spend exceeds $150,000 fifteen days before your next bill date, you will be auto-upgraded to the Full Suite Elite plan ($1,748 per month). You will see an immediate charge detailing out the prorated cost. In this case you'll see a credit for 15 days of unused time on the Pro plan and a new charge for the remaining 15 days on the Elite plan. From there, your subscription will continue on the Elite plan and use your original bill date.
If you choose to not renew and cancel your subscription, you will retain access to AdStage until the end of your billing period.