Photos are randomly vanished

I don’t know why but my photos got vanished for no reason . I never deleted it and I never give my phone to anyone. I have iPhone 15 I just got this message phone in December 2023 it just five months and it has issue. I tried to contact them before about my Apple ID . It shows some random Apple ID on my phone that I never had I can’t even update my apps because of it . And now there is one more problem with this photo thing . And my problem is not Been resolved. If I invested 1280 $ in this phone you guys can’t even provide a good service. This is not fair . In that photos I have my documents , videos , photos of my first ever trip . You have to deal with this issue no matter what I want my photos back . Please