I like to use tawk.to . The chat service is free and very customization to match the theme on your website. They have an agent "add-on" for $1/hr. All you have to do is give them the tools / information on how to answer your user's questions and they will take care of it.

I think Chat has proven to be an excellent tool for supporting our customer and client. I also use live chat for web development company Mujadidia Inc.