Treat him/her as you would like to be treated in this kind of situation. How would you like that someone else tell the exact same thing to you? Right there... your answer ! =)

I do not like to ignore the others to know that I don't want to talk with them any more, soi prefer i tell him\ her that a nice way

i just keep my teeth together for that kind of action they will know it, that i don't want to talk to them. cowboy...

Just say, I'd love to keep chatting with you, but I've got to go to................. Can we catch up later? Bye for now.

to be a polite answer it has to start with sorry.....and it goes like this : ,, sorry i can not talk now``, ,, sorry i am busy``, .....etc