Bar the hinge, there are no moving parts on the fold/flip, so what could be creaking, I have no idea
Is it every single call regardless of your location.
.....
If I helped or solved your problem, please like or tick solved.
Have been using phones since 1993, and am self taught.
I offer advice for free, cos I think it'll help, if it doesn't, explain why, I might learn something new too.
Current phone Galaxy S22 Ultra
Previous phones: most S series, Note 2, Samsung Alpha, iPhone 3gs, far too many Nokia's!