Koongo app is charged within the Shopify billing system. The 30-day free trial period is activated by Koongo app subscription confirmation. You can find more information at Confirm Subscription Plan

The first payment is charged after 30 days

Koongo app's first payment is charged after 30 days from the date of Koongo trial activation. You can increase or decrease the Koongo subscription amount during the trial period.

The last confirmed subscription amount is charged at the beginning of the new app payment period. If you cancel the trial period prior to the 30-day period end, there will not be any Koongo fee applied.

How do I cancel the trial period?

If you cancel the trial period prior to the 30-day period end, there will not be any Koongo charge.
You can cancel the Koongo app trial by uninstalling the Koongo app in your Shopify store.