Who I have the same questioned this topic

I am not receiving phone calls from businesses I work with.  I have no numbers blocked on my phone or account.  This is a recent problem.  Example:  My alarm company calls me when there is an issue with the alarm.  I am not receiving these calls - they are not showing up in my recent call list and my phone is not ringing - no voicemail shows up.  They say that it goes to voicemail after ringing a few times.  My phone has been updated and restarted, network settings reset, do not disturb has been deactivated.  I have researched for days and nothing has worked so far.  I have an iPhone 8plus.  Any help will be greatly appreciated.