I implement the example from facebook credits, and create an test app, added the callback.php in the Callback Url, place my keys correctly. but I get this error:
Sorry, but we're having trouble processing your payment. You have not been charged for this transaction. Please try again.
I am trying to create a few buttons with different monetary values. Like:
Click to get 100 credits
Click to get 1000 credits
If I use this generic code, I get the payment window just fine, but I can't see my products there, I can only choose from already made presets :
function buyMore(){
    // calling the API ...
    var obj = {
        app_id: 'xxxxxxxxxxxxxxxxxxxxx',
        method: 'pay',
        order_info: n, 
        purchase_type: 'item',
        credits_purchase: true
    };
to show the user my monetary presets I think I need to pass different values to the function:
<p><a onclick="buyMore('100'); return false;">Buy More Credits 100</a></p>
<p><a onclick="buyMore('1000'); return false;">Buy More Credits 1000</a></p>
function buyMore(price) {
    var order_info = { 
        "title":'title',
        "description":'description',
        "price":price,
        "image_url":'http://....img_url',
        "product_url":'http://....product_url'
    };
    // calling the API ...
    var obj = {
        app_id: '153230661424821',
        method: 'pay',
        order_info: order_info,
        purchase_type: 'item'
    };
}
Not sure if I got it right.
Can anyone push me in the right direction?