Depending on the issue you have, when contacting support you might be required to provide the support agent with your Client ID. To get your Client ID follow these steps:
Open the game and log in to your account.
Log in to one of the servers you already have a character created
Select the gear icon on the top right of your screen to open the game settings
On the settings page you will see your Client ID on the bottom left corner of your screen right above the Device ID.
Press copy to get your Client ID and send to Support