After logging into TIKR, click on the gear in the top right corner and select "Subscription and Billing"
You can directly cancel the subscription from this page. After cancelling, you will continue to receive the service through the period that you have already paid for. However, the subscription will not renew after that period.
We are sad to see you go and would really appreciate you sending an email to us at firstname.lastname@example.org letting us know how we could have made your TIKR experience better :)