If you start a free trial, the free trial begins before you are first charged, so there are no payments to be refunded.
You can have 7 days of trial for any premium plans. You will not be charged if you cancel your subscription before the trial ends. So, it's totally risk-free.
For example, if you used 5 trial days for the Essential plan of $4.95. Next time if you try the Growth plan of $9.95, you will have 1 trial day only. In case you already used up all the 7 days in one time, the next time we save 1 day for you.
To keep track of how many days you have left, you can see the message at the bottom of any page.