Simvacy numbers are designed to work only on your messaging apps, and for privacy and security reasons, incoming calls outside of these apps will not work. To make secure calls using your Simvacy dialling in or out will only work "in-app" such as calling via WhatsApp, Telegram etc.
We have a voicemail-to-email feature so that anyone who attempted to call you without using WhatsApp, Signal etc, will be able to leave you a voice recording which is then sent to your email address registered to your account. From there, you can choose how (or if) you want to respond in your own way.