All of a sudden my all incoming calls are going straight to voicemail iphone 12 pro

It’s a glitch with iOS 17 and up. Try toggling airplane mode on and off on your iPhone and then you’ll see the signal bars on your iPhone to be active again. You’ll now be able to receive calls. Hopefully Apple will fix this glitch in iOS 17 and up. Hope this helps you.

Since voicemail is a specific cellular carrier service/feature, I suggest that you contact them and and check your configuration.

Regards

Giulio