Incoming calls go straight to voicemail sometimes

Can anyone let me know why sometimes incoming calls go straight to voicemail without ringing on my mobile device? Sometimes, I get a notification that I missed a call while my iPhone 8+ is just sitting on the desk waiting for calls in the WiFi environment. Is anyone experiencing the same?

Spam Call???

We’re getting the same thing - searching these forums for a solution (there appear to be a number of posts on this subject)

Having the same problem. Tech support has no idea how to fix it. I suspect the Android app is the problem. 95% pf incoming calls go straight to voicemail, phone never rings.