by aviplugins.com on WordPress.org
User support plugin. Registered users will be able to create/ reply support tickets. Admin can reply on the tickets from admin panel.

Support tickets listing in admin panel.
Use this plugin to create your very own customer support system. Let customers of your site to generate a support ticket whenever they require assistance from you, and you will be able to solve their issues by posting replies to the tickets. The customers will get email notifications when you post a reply message to the ticket.
There is a PRO version of this plugin that supports additional features. You can get it here in USD 2.00
Post your plugin related queries at https://www.aviplugins.com/support.php