You don't need to enter any payment details to activate a free trial. If you like Aria, you can enter your payment details at any point during the 30-day trial. If not, simply stop using it and we'll delete your data once the trial has ended.
No. Aria is a pay-as-you-go subscription service. There are no long term contracts or commitments on your part. You simply pay month-to-month (or you have the option of making a yearly payment). If you cancel, you'll be billed for the current month, but you won't be billed again.
If you upgrade from one plan to another you are not eligible for another 30-day free trial. The 30-day free trial only applies for when you sign up for the first time. You can upgrade or downgrade your plan at any time.
No. The prices you see above are all inclusive. For example, the "Large" plan is $100/month for 150 to 200 users. That means you pay $100/month total no matter how many users you have as long as it's 200 or less.