If they ask for your name, you give them whatever you want to be called. If they ask for an English name after that they are just rude. If they first ask for your english name, i think they are again being presumptuous. Just respond with whatever name you want to be called, even if it is difficult - just don't fuss too much if they can't pronounce it correctly - unless they are really trying honestly to get the sound right.

Unless there's compelling reason, it's off-putting to native speakers when foreigners use English names instead of their own names, because it appears as if they are trying to hide something. Our culture values authenticity, so be proud of who you are by keeping the name your parents gave you. It's also ok to go by your last name. Just be yourself.

Is your family name easy for English speakers to spell and pronounce? If so, I would just use it. You could say "my name is Wong" or whatever. People might ask for your last name and you could say "Just Wong." The point of an English name is to make it easy for people to pronounce and remember your name.

That seems alright to me. Just say "Please call me by my family name, -----". But I have to ask, what's wrong with your Chinese given name that you don't want people to use it?

Is your family name easy for English speakers to spell and pronounce? If so, I would just use it. You could say "my name is Wong" or whatever. People might ask for your last name and you could say "Just Wong." The point of an English name is to make it easy for people to pronounce and remember your name.