Handfull of company phones go straight to voicemail

Hello. It seems you've already done some great troubleshooting, but a call in to our Mobility team may be in order here. They'll most likely have to refresh some network profiles (basically a reboot on our team's side). It definitely is an odd situation as it happening in multiple locations suggests a hardware or SIM issue, but since there are three different devices, etc. that may be unlikely as well.