You can cancel your paid SERP Bots at anytime and you won't be charged for their services again, however they will still work their notice of any remaining subscription days, so no refunds will be given for remaining usage.
To cancel just visit the
team management page and in the lower part of the screen you will see all of your bots and you can click the red "Cancel Subscription" button for each bot you wish to cancel.
If a bot is not set to auto renew or has already been cancelled then there won't be a cancellation button and their details will show a "Contract expires" rather than a "Contract renews" date.