One possible cause has to do with Call Transfer and failover. If the person who answered the call from a failover node (or different node) and they transfer the call. The call will now show as if the transferrer was the caller (not the original caller).If the person who initially answered the call was a SIM Ring Device under a routing user, the voicemail will show it's from the routing user.The solution is to verify all devices are registered to the same node.