Crackling background sound during calls!

Please help! I have an iPhone 14 Pro and i hear loud crackling background sounds during normal calls. However, this does not happen with calls made through watsapp. There is no issue watching videos or listening to music. I have tried everything from resetting my phone to factory settings, downgrading my iOS to a previous version, hard reboot, etc. During calls, when this happens, if i switch to speaker, the crackling stops momentarily. But it starts crackling again, and then i switch back to normal iphone and it stops again momentarily. I have to keep switching back and forth between speaker and iphone to be able to hear the other person properly during these calls. Its not a network issue and i dont think this is a software issue either. Any advice?