How do I cancel my Conjured Referrals account?

All you have to do to cancel is uninstall the app from your Shopify store's settings > Apps and Sales Channels, and just click on "remove".

If you don't want to lose all your data, you can alternately go to your App Subscription and scroll down to see the Freeze the account option. This will prevent any further billing, but allow you to keep the app installed until you're ready to use it again.