A full version app for Android, by Appenza Tech.

Call Without Internet – PTT Walkie Talkie Lite is an application that allows you to make free phone calls and talk with other people using the Walkie Talkie method. This is a simple method of communication where the users can talk to each other directly, regardless of the number of devices or networks that are involved in the communication. 

If you want to use this application, you just need to download it on your device and then you can use it to talk to other people. The app does not require any special configuration. It works in a simple and easy way. All you need is to install the app and start talking. The app is completely free and does not have any in-app purchases.