Budget Dialup is a prepaid service, so there is no need to cancel your account; simply stop using the service. However, make sure you check the following when you decide to stop using the service:
Log in to the Member Site.
From the links on the left, click Automatic Billing.
Make sure Automatic Billing is turned OFF.
Any time remaining in your account is available for use until it expires and you can always come back and start using the service again at any time in the future.