Forget about messing around with apps. There’s a powerful voicemail handling system built into nearly every big carrier today — and that system almost always includes a system for recording a voice message and sending it directly without ringing the target phone. I will walk you through the process of doing this on Straight Talk (since that happens to be my carrier) but most carriers will have similar systems.
A VPN service provider offers the users the means to get anonymous online and protects their data. They offer various packages for their users. Since this is offered online, the customers can contact at any time, literally! Here is an example of a script for a VoIP phone service for practice.

If all those steps fail, a reboot may be in order. If you have tried Airplane Mode, deleted the voicemail message, and cleared old messages, this is the next task. Try a simple reboot to see how it goes.
You will be asked to delete your current Voicemail greeting. Click on the ‘Yes’ button that appears on the screen if you want to remove that. You can save your new recorded Voicemail greeting or can use the default recorded option. Wait and hear the new Voicemail greeting message that the instructions speak out. If you want to keep that recording as your Voicemail greeting, then save it. Or you can re-record the message to get a different greeting.