偽黒電話 - 昭和レトロなダイヤル電話

Insert your finger into the hole corresponding to the number on the dial and rotate it until you reach the pin position.
The dial will rewind when you release your finger, so enter the next number.
Once you have finished entering all the numbers, press CALL to activate the phone function on your smartphone (iPhone and Android), allowing you to make calls.
Register phone numbers in the phone book function, and when you select one, a guide will appear in the hole.
Since only that number can be called, you can make calls with peace of mind.

It is currently available for free (with ads) on the App Store and Google Play.