ub for sub is an Android app where users can promote their YouTube channels to get more real subscribers and achieve their goal. We have made an app using YouTube's official data api v3, along with in-app purchase and a credit system. Users can get credit by subscribing to other channels, and in this way this way they can promote their own channel using the credit. And we also implemented a live chat system, so if the user has any issues, they can directly contact you through live chat. fFulldocumentation available