Using name and not Default Name

We are using StickIt in our 4 computers.
For Example: one computer has a name Terminal 4, used by John, with ip 192.XXX.XXX.XXX.

I have added John at my stick contats, using his name and ip.When I received a message from him, it came with Terminal 4 name and not John, and when I?m going to send him a message, I have John and Terminal 4 with same ip added at my contats list. How can I exclude Terminal 4 and use only John ?

Best Regards,