A man I don't know calls me and starts talking to me in Chinese. All is fine, except I don't know who he is. I sense I'm not the person he's looking for. How do I ask who he is without being too blunt: "你是誰?"
There are several ways to say it:
Qǐng wèn (May I ask), nǐ shì (you are) nǎ (which) wèi (identifier for people/position)
May I ask, who is this?
Nín hǎo (hello), nín (polite form of you) zhǎo (looking) sheí (who)?
Hello, whom are you looking for?
Wei ("hi"- typical way people answer the phone), qǐng wèn nín shì sheí?
Hi, who is this please (..., 请问 is "please". 请问 ,... is "excuse me") ?
Wèi nǎ wèi
Hi, who is this...?
Zhǎo sheí ya ("ya" is a participle equivalent to 啊 "ah" expressing surprise or doubt)?
Who are you lookin' for?
These are the ones I typically hear... although there are more.
Some people (at least in Taiwan) also say (你)哪里找, which to me doesn't seem either super polite or super impolite...really just depends on tone of voice.
Alternatively, you could politely ask him who he is looking for:
(Side note: I'd also like to point out that