Click the link below to go to our free domain checker which will be able to tell you all the details about your domain:
https://www.smallbusiness.host/clients/domainchecker.php

Type your domain into the search bar and hit the button 'Check Availability'

This will give you a list of associated domains. Click the 'WHOIS' link next to the domain and this will tell you the registered details for the domain.

The 'Registrar' is the information that you are looking for.