i considered posting this in xx/xy, but since it's not trans-specific (i'm not out at work) i thought i would post here. at work i go by a gender-neutral variant of my legal name. for the most part this isn't a problem - there's a few other coworkers who go by variants of their legal names, and one who uses a completely unrelated name, and no explanation has ever been asked. everyone from my district manager on down uses my proper name, except one coworker. at first, said coworker seemed to find it funny when i got annoyed at him. i reined in my annoyance and switched to calmly asking him not to. then i started trying to completely ignore him when he used to the wrong name, except we work in a coffee shop and usually when he's asking me something ignoring him would mean ignoring the customer too, which i can't justify. he's justified it in part because it's my "real name" and "isn't that what your parents call you?" (yes, my family and no one else gets to call me that, since they've had 20+ years of calling me that). he also seems to just plain default to it and not even be calling me my legal name to annoy me. i don't want to go to the manager about it, because without the explanation (trans) it sounds kind of petty, but i'm also not sure what else to do. so, any advice?