You can cancel your subscription by logging into your BURST account on the BURST website.
Once logged in you will see the person icon 
This will bring you to your account and from here you can manage, add and cancel your subscriptions with BURST.
Canceling a subscription from a Laptop/Desktop:
Once logged in you will see the person icon in the Right-hand corner, This will bring you to your account and you can then select the My Subscriptions tab from here you can select edit and then remove to cancel your subscription
Canceling a subscription from a Mobile device:
Once on the BURST website, you will see the Menu in the Left-hand corner, select this, and then account, you will be brought to the log-in option, once logged in you must navigate back here and select the Account.
This will bring up your account and you can view the My Subscriptions tab from here you can select edit and then remove to cancel your subscription.