Setup a VPN back to your home country.... Use that to complete billing.
The systems most likely freeking out because your making payments far removed from where your card says your from. And just handling it badly rather than making the problem clear. I have similar issues as I internet via satelitte uplink that relays against multiple ground stations that can make me appear to be connecting from a different country every few hours or so.

Sorry, would have posted this yesterday.. But the daft post limit is a thing.