The process for a remote payment (PayPal, WorldPay, 2Checkout), is that we send the user to their page with the amount we wish to charge, and they fill out the payment information. The payment provider will then visit our defined postback url (for Gossamer Mail, postback.cgi) and depending on the payment provider will report a different status (valid/success, pending, etc). Until we get a success report, the user's account won't be enabled/renewed.
Adrian