Hey Sybot2020,
Welcome to the Apple Support Communities! Thanks for your question about you calls going straight to voicemail. I'd be glad to see what I can do to help you out with this.
You've done a great amount of pre-work, as those are all items I'd check too. You mentioned updating iOS. At that time, did you also update the carrier settings for your provider? If not, that'd be a great step to take. Look over Update your carrier settings on your iPhone or iPad for a little more info on that. If that's all updated, check to see if you're using any call filtering apps that could be getting in the way of calls coming in as expected. A few examples of apps like that would be RoboKiller, TrueCaller, Hiya, Mr. Number, and others.
If you're all clear there, you may want to check with your carrier to see if they have a service or feature that can block spam or unwanted calls. Something else to check is to make sure that in your area you have good signal strength.
Report back what you find out, and we'll see where we are at that point.
Be well.