Hi, When the person calls you, they may say something like: "May I speak to ___?" "Is ____ home?" If you don't know that person, the best responses would be: "May I ask who's calling?" "Can I ask who's calling?" "Who am I speaking with?" Once the person says their name, you can respond with: "Yes, this is ____." "This is _____. How can I help you?" You may also want to know how to ask for a person's phone number in case you need to call them back: "May I have your number?" "What number is best to reach you at?" Good luck! :)

When you know who is calling, you say the statement "hello" or "hi". When you don't know who is calling, you ask the question "hello?" or "who is this?".

Yes you can say; May I know who I talking to?" OR Hi this is ........., who's speaking?

DON'T say "Who are you?" It sounds very, very rude. You need a certain amount of politeness on the phone. Use "Who is this?" or "May I ask who is speaking?" as a start. The other answers are also full of excellent options.