There are in fact a very limited set of circumstances in which a name change can now be granted, such as when privacy concerns arise. This appears to be one of those times.
Please send a handle change request through the Contact FitDay link at the bottom of the page (email@example.com). It may take a couple of weeks, as it has to be done by a technician and in two databases.
And for future reference, accounts can be disabled upon request to the same email address, and it also takes some time to go info effect.