Ye' old general discussion board. Basically, for everything that isn't covered elsewhere. Come here to shoot the breeze, shoot your mouth off, or whatever suits your fancy. This forum is not for asking programming related questions.
You want to hide the payment method from the user? Unless they provide an application of some sort for you to use on your website, I don't believe that is possible. You could send the value to their page if you find out how their forms determine input.