When you’re logged in, be sure that the mobile line displayed is the one with the iPhone voicemail password you want to change. Then follow these steps: Navigate the website starting with: Phone/Device -> Reset Voice Mail Pin -> Highlight your mobile number -> Submit; Once again, you’ll see “Password Incorrect – Enter Voicemail Password.”
Access to voicemail can also be obtained through the iPhone’s dial pad by pressing and holding down the 1 key until your phone calls your 10-digit phone number, or by pressing the voicemail icon, which can be found in the bottom right corner of the dial pad screen, as shown in the image below.

To use a different greeting that you already recorded or switch back to the default greeting:
"The High Representative noted that while disagreements still persisted, the EU and China needed to continue engaging intensively in a number of important areas," the EU said, adding Borrell underscored the inclusive and cooperative character of Europe's Indo-Pacific strategy. The EU is taking a softer stance on China, one of its most important trade partners, than the United States which has struck a new security deal (AUKUS) with Britain and Australia that is widely seen as designed to counter China's growing assertiveness in the Pacific.