All payments are final, so If your Vsble PRO trial has expired and you have upgraded to Vsble PRO, you can not downgrade to a FREE trial instantly. You can cancel your PRO subscription and it will simply expire & downgrade at the end of th billing period you have selected ( after a month, or a year). It will not auto-renew, and at the end of that billing period you can then downgrade to a FREE plan.
The reason why we do not provide endless immediate downgrade option after you have booked a PRO plan, is that it would increase dramatically the bureaucracy, as theoretically you could upgrade, downgrade, upgrade downgrade 100 times. As a company we have to plan ahead. Therefore we provide an entirely free plan and a 14 day trial period, so you can commit to a subscription if you like. If you are not yet sure, choose monthly payment and update it to yearly, once you are sure.
To cancel your PRO subscription follow the "How to cancel my PRO Subscription" guide.