internal microphone not working on iphone 15

i recently noticed on the off brand pair of headphones i have, the

microphone is horrible. i thought it was the brand, because the other pair i have (it came in a two pack) doesn’t work either. the headphone audio is fine, it’s just the microphone. i tested it out on my roommates phone, the 15 pro, and hers worked fine. i’m unsure what to do as it’s only two months old, and only been dropped twice, but not hard at all.