Are you talking about some specific implementation that you want? Because I know when I miss a call on iOS... Edit: they want the "Repeat Alerts" setting that

Are you talking about some specific implementation that you want? Because I know when I miss a call on iOS... Edit: they want the "Repeat Alerts" setting that "Messages" has but for "Phone" which is missing the option. Settings > Notifications > Messages > Customize Notifications > Repeat Alerts