How are the international calls billed for a pre-paid anual account? Do I need to have positive redit balance to continue after 60 min. allowance? If so, is it taken from credit balance right away? If not, is it billed monthly to credit balance or credit card?

When I took the advange of propmo pricing on my anual account, the money in credit balance (from shipping HT502 back) was not applied. When is this balance applied?

Thanks.