You can use our contact form ("Contact" link at bottom) for private information (of course not the credit card itself).
I have checked and seen the 4 attempts but all 4 got declined by your credit-card issuing bank.
Best is (as should be written in the error message if you choose to come back to our site after the unsuccesful payment attempt) is to contact the 24/7 phone number of your credit-card bank and to ask them why they are declining your transaction.
Usually, that's enough and a few minutes later you can do the transaction.
If you have any issues after that, please use our contact form to let us know. Alternatively you can try paying with your credit-card through paypal or 2checkout (no account needed).
I apologize I didn't realize I was giving away confidential information.
I looked around for a direct contact form but couldn't find one until just now. Now I see it's the link at the very bottom of the page. I called the bank and they are going to authorize international transactions I think that will fix the problem.
No worries, i edited your message to make the private information private
yes, our headquarters are located in Switzerland, so that's probably the issue you had. If you buy with your credit-card through 2checkout, they are located in US, and your national card should work there.
Just out of usability curiosity to improve our site, where all did you look for the contact page link on which pages? (so maybe we can add a second link at one of these places)