Okay, and?
Just because you said a word that someone Muslim would say when they're telling the honest-to-god (or in your case honest-to-Allah, no hate to Muslim people) truth, you could still be lying. If you want people to stop calling underage, you need to take responsibility and change your act up a bit. Perhaps be more mature and tolerant towards a singular swear word, and not harassing someone for it?
Also, stop using outdated, stolen comebacks. You can use them to inspire new comebacks, but it's unoriginal, and it only further suspects you of being underage.
If you have proof of yourself being 13+ years old, perhaps we won't suspect you of being underage.