No. Never. Not a chance.
If you pay up front for any subscription, that specific account will expire on it's own after all of the months have been shipped. You will never be charged again unless you want to continue the subscription. And believe us, you'll want to keep the socks coming!
Note: If you cancel your subscription at any point during it's active months, no future shipments will be sent. For example, if you cancel your 6 month subscription in month 4, the remaining 2 months will not be shipped.