You subscription and billing settings belongs to your Workspace.
In order to find the settings click on the Menu in the top right corner of the app and select your workspace:
Click on the workspace to select it in the menu:
In the workspace view menu on the left you find "Billings":
Clicking on "Billing" to open up the payment portal (operated by our payment partner Stripe).
You will see you subscription details and a button with the text "Cancel Plan". Click on the button to cancel your plan.