1.) If someone asks what you were ‘born as’, tell them it doesn’t matter. If you tell them the truth, they’ll insist on referring to you as such.
2.) If someone asks what your ‘real name’ is, repeat the name you already gave them. They don’t believe your name is real because you chose it.
3.) If they persist and say ‘no, what name were you born with’, tell them it’s none of their business. Or they’ll insist on referring to you by your old name.
The plaintext is advice, the italics are the reasoning that runs through my head at the time. Unfortunately in many cases the italicized section is not true and the person is just curious and doesn’t understand why these are rude questions, but you can’t tell that until you give them a chance to act like an ass - which means you might then have to deal with someone being an ass, natch. It’s so much easier and feels so much safer to just be jaded. The italicized text has been true too many times.