Being trans myself, I will gladly tell you no one can change their biological sex yet (meaning, reproductive sex). I do hope science gets there though !

I don’t even think anyone can change their gender ! Some people’s gender changes on its own, but I’ve just always been a woman ; and most trans people are like me.

The thing we actually disagree about is whether someone’s gender and biological sex can be separate. But it’s just a scientific fact that they are.