Warning Do not purchase Nx with Nx credit anytime soon
A lot of people haven't received their nx and have waited whole days.
Also, make sure to uncheck the "save credit info" everytime you purchase online, it's way so insecure and doesn't verify any security information before the purchase is complete.
Proof of issue:
http://maplestory.nexon.net/Community/#%2Fshowthread.php%3F443377-Credit-went-through-but-it-Doesn-t-Show-in-Account%26p%3D3621822%23post3621822
July 11, 2012