Cancelling is a simple process. First, log into your Client Area. Once logged in, follow these steps:

Click on "Active Services".
Click on the small arrow next to "View Details", beside the service you wish to cancel.
Click on "Request Cancellation"
Describe the reason for cancellation (optional)
Choose either Immediate (meaning the service is cancelled now) or End of Billing Period, meaning it's cancelled before the next renewal date.
If you have a domain name purchased from us, you can optionally check the box "Cancel Domain Renewal?" to cancel renewal of that domain as well.
Should you have any questions, please contact our support@jdchost.com.