This permanently removes the voicemails from your phone so should stop notifying you.
After setting the number on your voicemail, you must also record a personal voicemail greeting. Follow the steps below. Start the Phone app. if you don’t see the numeric keypad, tap “Keypad” at the bottom of the screen. Tap and hold the “1” for about two seconds until the phone automatically calls voicemail. Immediately tap “3” to access voicemail settings. Listen to the options. On most voicemail systems, tap “2” to start the process to record a new greeting. The current personal greeting will play; then tap “2” again to record a new greeting. Say the greeting you want, and tap “#” when you’re done. To save the greeting, tap “1.” The personal voicemail greeting has been set. Hangup the phone. How to setup voicemail using a Visual Voicemail Applications

The service also recommends stating your name, apologizing for missing the call and that you will call them back. If possible include a time frame for a return call. Don’t ramble or include un-needed information.
1.) Вы подключены к почтовому ящику Васи Пупкина. В настоящее время г-н Пупкин вне зоны доступа. Вы можете позвонить позже или оставьте сообщение с вашим именем и номером телефона, чтобы Г-Н Пупкин мог перезвонить вам как можно скорее.