What is JotForm?
JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
At JotForm, we want to make sure that you’re getting the online form builder help that you need. Our friendly customer support team is available 24/7.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
Yes you can, here's a guide on how to upgrade: https://www.jotform.com/help/331-How-to-Upgrade-My-Account. You can choose monthly, yearly or bi-yearly plans. In your case, you need to select monthly plan. You will then be billed on a monthly basis. To stop your subscription, simply downgrade back to "Free" plan before the next billing date.
To downgrade back to "Free" plan, you can follow this guide: https://www.jotform.com/help/341-How-to-Downgrade-Subscription-Back-to-Free-Account
I hope that helps.