But what’s really great about Samsung’s way of dealing with voicemails is the new and improved Visual Voicemail service. This lets you view voice mail messages and listen to them in any order you want. Instead of listening to all of them in order, you can pick the ones you’re interested in. Even more, you can decide to erase or archive them, all from your device screen. Visual Voicemail also includes button shortcuts to call back or text a person that left you a voicemail.
How how how can that be??!! This is the year 2016, and I can’t set basic options like the number of rings! Actually I too want to turn off voicemail completely. I am aghast to read I don’t have a choice.

On the iPhone, go into voicemail and tap "Greeting". Record a few seconds of something and tap stop. Before you tap save, use iFuntastic or SFTP to navigate to /var/root/Library/Voicemail on your iPhone. You'll see a file called "Greeting. amr". This is the audio you just recorded. Delete that file and replace it with your custom message which should then be renamed to "Greeting.amr". Tap "Play" on the iPhone to verify your message works. If it plays, tap "Save" and your custom message will be uploaded to AT&T's servers.
It’s a good practice for each of your team members to have their own personal business phone numbers. There are many reasons why they shouldn’t use their personal cell phone number for business, so you’ll want to give them their own phone number through your VoIP provider or phone system.