Guess this time my ticket got answered immediately:
Hi JOHN DOE,
Thank you for contacting Frontier Support regarding the Store payment issue.
I am very sorry you are having this issue but I wanted to let you know that we are aware of an issue that our current payment provider doesn't support payment from your location.
If you are attempting to purchase digital game extras, we would suggest that you temporarily change your store address, to the UK.
To change this, please can you log into the store - https://store.elitedangerous.com/. Once logged in, please navigate to Account Information and select addresses.
Once you have successfully completed the purchase, please change this back to your current address.
I hope this helps, and if there is anything else that we can do for you please give us a shout.
Fly safe Cmdr!
CMDR Ariane
Elite: Dangerous Customer Support Wing
Your Frontier Developments Team