If you are in trial mode, canceling your trial is not a self-service option. If possible, allow the trial period to expire and your account will be automatically cancelled.
If you are in a paid subscription, as an account administrator you can login to the Administration Portal and navigate to the Plan Subscription section. From there you can cancel your subscription.
Note that once you cancel your account, you will not have access to the FastField apps or our API, but you may continue to access the Administration Portal to collect your data if needed. After 90 days, we will permanently remove all of your data from our system.