Signup for Zoho Support Free plan

Signup for Zoho Support Free plan

I have a Zoho account (user name) created when I signed up for CRM.  I want to use Support Free Plan
If I'm logged in, and I go to  https://support.zoho.com/, I'm directed to a page to " Sign Up for  Enterprise Plan".  If I'm not logged in and go to above url, and then go to Pricing and Signup page, and click SIGN UP NOW under free plan, I'm directed to  Sign Up for  Free Plan page, but if I enter my user name, it complains  This User Name is not available . 

How can I get Zoho Support Free plan with my existing user id?