If you’ve already created a custom voicemail on your iPhone, you can tap Play to see how your voicemail sounds. If you’re interested in creating a new message, tap the Custom button. From here, you can start recording your message by tapping Record and tapping Stop whenever you’re finished. Once you’re finished recording, tap on Play to make sure the message comes across as you’d like and hit Save (in the upper right) to save it as your voicemail.
If you recently restored or updated your iPhone, your network setting may have been affected and may be causing “iPhone voicemail error try again later.” Please reset your network settings. Go to Settings > General > Reset > Reset Network Settings Enter your password. Press Reset network setting in red font. The phone will automatically reset it. After it restarts, your phone then tries voicemail again.

2. Make a call. Now that your phone has been activated, you’ll need to make at least one call before using your voicemail. That call can be to anyone, whether you catch up with an old friend, make your mom’s day with a chat, or just call your home’s landline.
Step 2: If your phone is able to use Visual Voicemail, you will see a Set Up Now button. If you don’t see this pop-up or your phone starts to call the voicemail, your phone will not be able to use Visual Voicemail at the moment. You can call your providers and see if you can get it if you want.