If your carrier supports the iPhone voicemail feature, you can retrieve and listen to your voicemail right from within the “Phone” app and call your contacts back by simply tapping their messages. That type of functionality is pretty neat and useful, because it saves you actual time. If not supported by your carrier, you will not be able to see the visual overview of your voicemail inbox and use any of the related features. Tapping the “Voicemail” tab in your “Phone” app will simply call the number associated with your voicemail box. So let’s get going with creating our custom voicemail greeting on iPhone! How to record your own Voicemail on iPhone Phone → Voicemail → Greeting → Custom → Record → Save
In your Phone app, navigate to the number pad. Pressing and holding the 1 key will dial you into your Voicemail's main menu instantly. You can also call your own number or select Voicemail from the list of options under the three-dot menu in the app. If this is your first foray into the matter, the friendly voice on the other end will guide you

Dial *98 from your U-verse home phone, dial your home phone number from another phone, or access your voicemail messages online from the Voicemail Settings tab. Press the * key when you hear your greeting. Enter your PIN. Press 4 and follow the prompts.
3. Enter your Pin Number. You will need to know your pin or passcode in order to check your voicemail. If you don't have this code, you will have to retrieve it from your carrier. You will hear instructions to input your pin. Hit the pound key after you enter your pin. Follow instructions on how to listen to your voicemail. It's usually to push a certain number (like 1). That's all there is to it. You should be able to hear your voicemail messages now.