Slydial only works if you’re calling a mobile phone. Even if the landline you are trying to call has digital voicemail, the app will not work. Otherwise, the process automatically bypasses the live line and goes straight to voicemail.
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

3.) This is the mailbox of Mr. John Doe. Please leave a message or call this number again at a later time. Thank you for your understanding.
You'll notice that many of these are targeted, but cover things that can easily annoy users. Slow keyboard response in Quick Reply is one of our frustrations with iOS 9.1 that this fixes. Other upgrades fix alarm bugs, iCloud backup problems and much more.