ReviewWheel starts with a 10-day free trial. You add a card when you sign up, but it is not charged until day 11.
Day 10 is the last day you can cancel without being billed.
If you cancel on or before day 10, you pay nothing.
On day 11 your trial converts to your chosen paid plan and your card is charged.
Separately, a 30-day money-back guarantee covers your first paid month. If ReviewWheel is not working out, you can request a refund within 30 days of that first charge. The trial and the guarantee are two different things: the trial is free time before any charge, and the guarantee is a refund window after your first charge.
Together that gives you about 40 days to try ReviewWheel with no risk. No contracts, cancel any time.