I would personally continue using WHMCS as a support ticket system. If you need to have live chat integrated, I would look at the Live Chat Addon that WHMCS offers.
You can see their addon here, http://whmcs.com/livechat.php
Also, a free source would be livezilla, which is very good, and offers unlimited chats and operators for no cost. They do have premium options though such as copy right removal and so forth. You can access their website here - www.livezilla.com
Hope that helps you out bud.