Couldn't receive serial code
The bad news is, I’m afraid the serial code is lost now. They don’t hand it out again because if they were giving out serial codes and they give one to the wrong person, say someone trying to steal the account by contacting support and saying they lost it, then they’ve muddied the waters as to who owns the account.
The good news is, you don’t really need it. While support will ask for it when you contact them it’s not required. They will establish ownership by other means. I think it’s main value is if 2 people are disputing ownership of an account with support, the one who has the serial code shows ownership.
ArenaNet Communications Manager
It sounds as if your transaction did not complete, and you cannot set up that account. Please contact Support by filing a ticket through the “Ask a Question” tab on that linked page. They will be able to assist you. For tips on what information to provide in a ticket — mostly intended for security reasons to establish that you own the account — please read this post and provide as many suggested details as possible to expedite the ticket.
Communications Manager
Guild & Fansite Relations; In-Game Events
ArenaNet