Outlook.com rejects any type of name including the word “BANKO”

I am trying to use Windows Live Domains (domains.live.com) to power my domain email using Outlook.com. I am unable to create any account with the word "Banko" (my existing email through my current provider is *** Email address is removed for privacy ***). I tried to create this account on two unique domains and altering the name "banko" with something else at the end (like additional letters and/or numbers) and the system still rejected it saying it was unavailable. I even tried to create a new regular @Outlook.com account and again the system rejected any combiniation which used the word "Banko" in the email address -once again saying it was unavailable. This is very unusual being that years ago I created an @hotmail.com account with the name "Banko" in it, which I still use today. It seems like the system presently is rejecting anything using the world "Banko" in it. Is there a reason for this -and how can this be resolved since "Banko" is my legitimate last name?

Thank you.

Jonathan Banko