We have developed an awesome website builder, at present we want some help to customize the back end with WHMCS.

The requirement]:

On registration page the user can select free subdomain folder name [it would be look like abc.mysite.com where folder name is "abc], then the WHMCS will assign pre-defined free hosting package. The user can move to builder section.

Anyone has idea how to do that or can help to configure WHMCS. ? Please suggest / help.

Thank you