Can’t update and might have a hardware issue

I’ve been trying to update my iPhone 15 plus to iOS 26.1 but it keeps getting stuck on the Lock-screen verifying the update,it disabled cellular data until I update so I can make any phone call or text unless im on WiFi,I’ve force restarted it several times,I’ve went to iTunes on my PC and tried to install it but keep getting error code 4000,I’m running out of ideas of other methods I could try,I asked the IOS Reddit and a person on there seemed to think it was a bad baseband chip,any advice