Joomla customization work -- 2

I have the site in joomla [login to view URL] I need a feature of voice and chat conferencing of admin writer and customer on the above site mainly voice(audio conferencing ) is there and small text user are fixed only three (writer customer and admin) it may be a free extension linked with my site that are open availble in market and customized it without video or a link where we can initiate the conferencing