Here's what you'll have to do to upgrade your plan while in the free trial:
First, you need to cancel your free trial. To do that, follow the instructions in this article “How to cancel my subscription”. Click here to check.
After canceling your free trial, you can upgrade your plan by purchasing a new subscription. To do that, you can access your Billing Page. Don't worry, if you start a new subscription, you won't lose any of your board's information.
Note: If you couldn't cancel your subscription, you can contact our Support Team to request the cancelation.