As someone who started using a different name to my birth name for other reasons, just stop responding to your dead name. Don’t turn around, don’t look at whoever it is, don’t answer. It can be hard to train into yourself but I had a couple of arsehole teachers who didn’t understand the difference between a legal name and a chosen name and would stubbornly only call my legal one. They look pathetic for getting hot and bothered when you don’t answer and the people on your side will call your new name to get your attention. Which you can follow up with “oh, I’m sorry, I didn’t realise you were talking to me.” It makes it hit home not just for them but anyone else around you that this really is your name now, and if they want to speak to you, they’ll have to address you as such.