You can change your username here: http://seekingalpha.com/account/edit_bio
You may need to fill out all fields to save.
You can email support anytime at firstname.lastname@example.org
After much frustration, I discovered today that editing my bio page doesn't work in my version of Chrome (64.0.3282.140). I was finally able to change my username by editing that page in Internet Explorer.
We have replicated the problem and it is in our backlog. We do not currently have an ETA on when a fix will be deployed. I will update you when we have a firm date. Thank you for reporting.
Customer support service by UserEcho