How do I cancel a transaction in Google Wallet that hasn't gone through yet?

Question

Payment systems

I placed an order for Humble Bundle yesterday. I decided to pay through Google Checkout.
There were no funds on the default card. And the transaction hung in the status "Not accepted".
If you look at the transaction details, you can read the following:

Failed to withdraw USD 15.00 from VISA xxx-xxxx. You must update your billing information within 7 days. Otherwise, your order will be cancelled.

As far as I understand, if I put money on the card, the transaction will go through?
What if I don't want to? What if I have already used another payment system? Or just changed your mind?
Something I do not see the functionality of canceling the order. Can someone suggest something?

Answer 1

Well, so in the Humble Bundle itself and cancel the order. And all...