The review team rejected our application wrinting this :
We have started our review, but we need additional information to continue. Specifically, it appears your app may access or include paid digital content or services, and we want to understand your business model before completing our review.
Our app is free and doesn't include any payement package or page But we are coupled to another application for the login. And this other application has a trial period and effectively needs payment after.
Do i need to explain in my app all the payment process of the other app ?