You are absolutely right. However some people have different dialects and styles. When they speak of, it sounds they are uttering mistakenly, but this is not true. Like the Europeans speak our beloved prophet Muhammad as Mahamed, they don't speak of this word deliberately rather it is their dialect that makes them pronounce the words differently. If some people call you as Khatija, they don't do that deliberately. Never take it seriously. You call khadija.