To cancel your Linux VPS, you will need to login to your Client Area and submit a cancellation request by following the below steps:
1- From the main menu, inside your Client Area click on "Service"
2- Click on "My Services".
3- You will find your active service list. On the right side you will see button called "View Details".
4- On the right side of that button, click on the arrow pointing down and choose "Request Cancellation".
IMPORTANT NOTE: If you have a PayPal subscription, make sure to also cancel it along with the service to avoid being auto-billed.