How Do I Change What Service Account I'm Logging Into?

[Seldi]

As title. Should be simple enough. Due to a snafu that support has decided not to resolve, I find myself with two service accounts: The original standard account, and a collector's edition account. Naturally, I want the boons of the CE account, and would like to start playing on that.

But how do I do that? I've logged in and out several times, and not seen an option.

(Note: I'm playing the PC version on a Windows OS)