To assist you in making sure you're responsibly blocking & reporting numbers as spam we have provided a reverse directory that you can have numbers verified against to see who is calling you from these strange numbers.
If a caller leaves a voicemail from a number that you're unsure of you can look the number up from within the voicemail left. The instructions below will assist you as an iPhone user to navigate this feature.
Firstly, you'll need to tap on the clock icon to view your call history. 
From there you'll need to select the voicemail or number that seems to be suspicious. 
To the far right, next to the delete option you will see an icon with three (3) dots. 
Once you click the menu button, you'll get a few options to choose from. Select "Phone Lookup" and you will automatically be brought to the YouMail directory via the app. 
You should be seeing something like this, where you're able to look at the number and even leave a report if you'd like. 
How To Use Phone Number Look Up On iPhone
