How to kill the voicemail facility on an iPhone XR? On an iPhone XR running iOS 13.2.3 and connecting to the mobile phone 
network using a number supplied by Three, how do I disable voicemail?

I have never actually configured voicemail, but whenever someone calls my 
number and the phone is switched off (which is most of the time), they hear 
a message giving them the option to leave a voicemail. I want the number to 
keep on ringing without being answered, or if they must hear a message then 
for the message to tell them the phone is switched off and that's it.

Recently I got a text message from Three itself saying they'd left me a 
voicemail, and I would like to delete that voicemail without setting up 
voicemail in the first place.

In short, I would like to kill the voicemail facility, deleting whatever 
may be in the box, without even listening to it and without setting up 
voicemail in the first place. How can I do this? If to kill it properly I need to set it up first and then kill it, how do I achieve that?
Step 1: Go to your home screen and tap on the keypad icon at the bottom.

Step 2: Once the keypad is launched, type ##002# and then click on the Call button. There is no cause for worry since the iPhone will not actually make the call, but will display the settings of your voicemail.



Step 3: You will be presented with three different messages


Voice Call Forwarding
Data Call Forwarding
Fax Call forwarding.


Do not do anything, but simply tap on the “Dismiss” tab at the bottom of the screen. You will have successfully disabled your voicemail for all types of calls.