If you get in touch with the customer services team directly using the online contact form they will be able to lend a hand getting you set up on a new account with a username of your choice.
If you get an automated email reply back directing you to the community or help pages, you need to reply directly to that email (even if its from no-reply) and one of the customer services agents will get back to you as soon as possible.
Alternatively, if you prefer support via Twitter, please tweet @SpotifyCares.
Something strange has happened. Get in touch here and explain that you can't connect your facebook to this account. If you get an automated response directing you back to the community or to the help pages, make sure to reply to it directly to speed things along.
They sent me a automatic reply (happened before and they never got back to me):
We just wanted to let you know that we're looking into your query and we will get back to you as soon as possible. To ensure that our reply reaches your inbox, add email@example.com to your spam filter's whitelist.
If you need immediate help, please check out The Spotify Community http://community.spotify.com/ for support from other users. This is also a great place to read up on any company updates that might affect your service as well as posting your own ideas and feedback.
You can also check out our Help pages http://support.spotify.com. The FAQs contain solutions to the most common queries and guides on how to use Spotify’s features.