All I know is that the EA game cards works.
You can purchase them online/digital delivery here:
but be warned, for some reason you have a freakin $65.00 daily spending limit on your account... (i think it's something to do with their 30-minute gurauntee + staffing issues.)
and more bad news...there is a $5 activation fee per game card you buy.
If you really want to buy some Cartel Coins and get in on the "fun" , and you don't have a Gamestop or EA retailer anywhere nearby, this is an option for you.
Unfortunately, it's $10 more expensive...
but it DOES work.
BioWare, we shouldn't have to resort to these kinds of shenanigans..