how do you deal with someone online who acts familiar with you, when they don't know you

[c=BF6900][i]this really pisses me off, especially online, someone who answers your post and acts familiar with you, as if they know you, when they don't know you. that really angers me.

can anyone answer and advise how to deal with it? because i'm starting to feel annoyed now.[/i][/c]