Method 1 
You still have access to the site.


Step 1  | On the old site, go to the settings menu

Step 2 | Deactivate on old site



Method 2
You don't have access to the site anymore.

Step 1. Login into the Member's Portal.
https://members.stylishcostcalculator.com/licenses/

Step 2. Deactivate the license.