Custom Android Softphone for Voice Calls

I'm looking for a talented developer to create a custom softphone app for Android. The primary function of the app will be enabling voice calls.

Key Features:
-Able to capture dtmf in live call
-Able to connect any sip Provider
- Voicemail: The app should have the capability to take voicemail.
- Call Recording: There needs to be a feature for recording calls.
- Conference Calling: The app should support making conference calls.

Design Preference:
The design of the app should be classic and simple. It should be user-friendly and easy to navigate, without unnecessary complexity or clutter.

Ideal Skills:
- Proficiency in Android app development
- Experience in building VoIP softphone apps
- Knowledge of integrating voicemail and call recording features
- Ability to create a simple, classic design

This project requires a developer with a solid understanding of voice call applications and a knack for creating intuitive, uncomplicated user interfaces.