How to visiters close the chat window on smartphones?

How to visiters close the chat window on smartphones?

The zoho Sales iq Chat is working fine on desktops, but when visiter use it on their mobile devices there is no way for them to close the chat window and then they end up leaving our site. Why is there no "X" for mobile users to close the chat? Can you help me make that possible on my chat? This is really effecting our drop-offs.
Thank you.