You cash balance represents the amount of money remaining from any subscriptions that have not been used or might have been prematurely canceled. You can use any positive cash balance to pay for new subscriptions. A negative cash balance would mean that you have (or had) an active subscription that has not been paid for one or more months. In this case, you will just need to make a deposit for the negative amount to bring the balance back to zero. If you no longer wish to use the service, you will need to formally cancel your subscription from the subscription management page: https://www.cameraftp.com/secure/SubscribeHistory.aspx