Billie Eilish isn't interested in keeping people around who shouldn't be a part of her life. That's why she's totally willing to do what it takes to remove those people when necessary. That's what she lets fans — and a certain someone — know in "I Didn't Change My Number."
"I didn't change my number / I only changed who I believe in / You were easy on the eyes ... / But looks can be deceivin'," Eilish sings in the second verse, per Genius. She later adds, "You got a lot of f**kin' nerve / I don't deserve, so." So, indeed! It seems pretty obvious that Eilish is finished with a possible past relationship of one kind or another and therefore isn't answering the person's calls — making them think she changed her phone number. However, she's makes it clear that this is the case because the person that she's dealing with is someone she won't put up with anymore (even if they are good-looking).
Eilish herself opened up about the song, to Spotify (via Genius), saying, "It's all about, 'You can't get me anymore,' where it's like you know what? I don't have sympathy for you anymore y'know? ... You got me at first but I don't care now. ... And kinda just your last straw and being like, 'I am confident in this being my last straw.'" Part of what gave her that confidence may have been two particular people in her life.
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