Irrespective of the plan that you tried out during the 15-day trial period, once it is up you will by default be set to the Zoho Social Lite edition where you can retain one Brand. In case you have added multiple Brands within this trial period, you will get to choose which Brand you wish to continue managing under the Lite Edition. You can however, switch to one of the paid plans (Standard Plan and Professional Plan) if you wish to add and manage multiple Brands.
In addition to that, you can manage all the Brands you have purchased from Zoho CRM. All the existing Brands you've set up within Zoho CRM or Zoho Desk will automatically get transferred to your Zoho Social Lite Edition.
Please note that this is possible as long as you are subscribed to Zoho CRM.