Autofill by Detecting Country Code on App Start

Question

Good Day, I am making a project in Unity Game Engine (Uses C#), I'm using firebase phone authentication SDK. Everything is working fine, but I need a new function. When user opens app and phone number field shows. I need some sort of API or if any way to get user's country code for example +91 +966 etc Any help will be appreciated. Thank you ahead of time.