Having trouble creating an Amazon account with exterior credit card

I'm not from any country that has ads on their Kindles, and I really wanted to jailbreak mine. The problem relies on adding credit card data to my Amazon account with an exterior billing address. When I try to add the test Mastercard (trying to follow the AdBreak tutorial by Dammit Jeff, it's denied). I don't know what to do any more, I wonder if someone could help me?

My Kindle is on version 5.18.1 and on air plane mode. I didn't do storage limitation yet because I don't have the account.