add subscription manually

[ohadpartuck]

Hi,
Most of my site visitors like to bill their credit cards for my site subscription over the phone.

Is there a built in method to manually add the transaction so that the subscription will be added (including expirydates, reminders and etc)?
I.E POST to the payment_gateway.php as if the costumer paid via paypal.

by the way, I also must find a way to do it securly so that hackers can't post this info also.