For that navigate to
"Configuration" -> "Live help configuration" -> "Chat configuration" -> "Online tracking"
and just edit "Which ip should not be allowed to chat"
Values can be separated by comma, E.g 1.2.3.*,188.8.131.52
Developing application takes a lot of time. You can support application by donating. There is no company behind this application and it takes away my free time. Every donation matters and does not matter how small it is!