Sworkit is unable to cancel your subscriptions for you. In order to do so, you will need to manage your subscription through Apple or Google using the instructions found below.
For iOS users: https://support.apple.com/en-us/HT202039
For Android users: https://support.google.com/googleplay/answer/7018481
For Web users: Log into the web app at https://app.sworkit.com, Go to the 'My Account' page and you should see a button to 'Cancel Your Subscription'