Besides creating an audio file in the right format (Adaptive Multi-Rate), you also need to trick the iPhone to upload your new greeting to the AT&T servers:
Change your iPhone voicemail greeting using the Phone app on your device. The Phone app is the one with the white phone icon in a green box. For many users, this icon is one of the four permanent apps on the bottom of the screen. Tap the Phone app icon to enter the phone application.
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Follow the carrier instructions and enter your Pin or other details if asked by the audio instructions. If you follow these above steps correctly, you will be able to disable the Voicemail on your Android device.
Your iPhone does have a voicemail password, but you only have to enter it once and many new iPhones set it up automatically. However, there still needs to be some form of authentication between your carrier and your iPhone to download your voicemails. Even though you don’t see it, your voicemail password still exists.
I still get the same issue. I called my voicemail. It's set up and I was able to change my voicemail like that and listen to my messages, but the visual voicemail on my iPhone doesn't show any messages and will not allow me to create a new voicemail like it use to. Every time I click save it says "Greeting save failed. Failed to save your greeting"
Before you change voicemail greeting on the iPhone, make sure that you have set up the Voicemail on iPhone. Because when you follow the below procedure to change the greetings of the voicemail, you may not found the Greeting option if you haven’t set up the Voicemail yet. How to Change Voicemail Greetings on AT&T, Verizon, T-Mobile and Sprint on your iPhone or Android mobileVoicemail Greetings For AT&T and Verizon Users:Voicemail Greetings For T-mobile Users:Voicemail Greetings For Sprint Users:Can’t Change My Voicemail GreetingCan’t Record Voicemail Greeting How to Change Voicemail Greetings on AT&T, Verizon, T-Mobile and Sprint on your iPhone or Android mobile
On Android devices above Android 5 (Lollipop), open the Phone app. Then, press and hold "1" to call your voicemail. Now, enter your PIN and press "#". Press "*" for the menu. Press "4" to change settings. Press "1" to change your greeting. Make sure to follow all the instructions.
And then select your language preference. Enter the name and greeting information before you tap on "Set Up Now" option in the middle of the page. Just follow the similar method to change the default voicemail on iPhone for the other carriers.
.To delete multiple voicemails, press and hold the first voicemail message, then “More items.”Select “Delete” then check the “I understand” box > “Delete.”How to Access Voicemail on Android?
6. Voxist: Visual voicemail you can read. Voxist presents your voicemail in the most accessible visual form. On one screen you will be able to get acquainted with all the messages and choose which ones you really need to listen to.
The voicemail section allows you to change your personal voicemail message. Until you set one, anyone getting your voicemail will hear the standard Phone.com voicemail message. It’s always a good idea to set a personal voicemail so your callers know that they reached you. Try and give them an idea of when you’ll get back to them. You have 3
If your voicemail has been set up and you are unable to change your greeting through the 'Voicemail' tab, dial *86 then choose option 4 to change. From a Home screen, tap the Phone app . If an app isn't available on your Home screen, swipe left to access the App Library. Tap Voicemail then tap Greeting …
To listen to a voicemail message, fromthe home screen select the Phone app. Note:Alternatively, you can check your voicemail messages byselecting the Phone app from the home screen >Select and hold the 1 key > if prompted, enter yourvoicemail password > follow the prompts tolisten to your messages.
After receiving his Bachelor’s and Master’s degrees in Computer Science he spent several years working in IT management for small businesses. However, he now works full time writing content online and creating websites.
From the bottom, click on “Voicemail.”Select a voicemail, then the three-dotted menu.
Website: https://www.xfinity.com/mobile/support/article/how-to-access-voicemail-android-phone
Please keep in mind that normal airtime charges will apply for the time you spend setting up your voicemail.