App Review Rejection for Guidelines 3.1.1

Hi all, Our app has been rejected several times without any clear explanation of what we need to do. The latest rejection reason is as follows:

Guidelines 3.1.1 - In-App Purchase and 3.1.3(c) - Enterprise Services

We noticed in our review that your app offers enterprise services that are sold directly to organizations or groups of employees or students. However, these same services are also available to be sold to single users, consumers, or for family use without using in-app purchase. 

When an organization or group buys access to your app's enterprise services, you don't need to use in-app purchase. But when providing access to an individual user, consumer, or for family use, you should use in-app purchase. 

To which we responded with:

We would also like to clarify our app and business model:

1) Our app is a free app intended for companies, organizations, and business owners. Individual users can sign up for our app, but with some restrictions. We designed it this way so that users can try our app before registering their company or business.

2) In the previous app version, we enabled users to subscribe and unlock more features within our app using our own mechanism. Hence, the review referred to Guidelines 3.1.1. In this version, we have removed the feature so that users cannot purchase any subscriptions.

Since users cannot purchase anything from our app, we believe Guidelines 3.1.1 should no longer apply for the app review.

But our app is still not approved. Instead, they replied with:

We are not able to provide feedback on app concepts or features, but we recommend evaluating your suggestions against the App Review Guidelines, as well as the Apple Developer Program License Agreement, and the Human Interface Guidelines.

Can anyone enlighten us why does the reviewer still referring to Guidelines 3.1.1 when there isn't anything that user can purchase from our app? And what do they actually want us to do?