To change your Garry's Mod server hostname, you'll need to follow these steps:

Step 1: Log into your Host Havoc control panel (https://gamepanel.hosthavoc.com).

Step 2: View your game service.

Step 3: Click on the 'Configuration Files' module.

Step 4: Open the server.cfg file in the text editor.

Step 5: Edit the hostname setting to equal whatever you'd like your server to be displayed as.

Step 6: Save the file.

Step 7: Restart the server.