Provide Seat based charging with InApp Purchase

Hi, as I checked now multiple threats in the internet I cant find a solution to solve the Problems with the Apple Guidelines.

Our Business Model is based on pay per user. As Apple rejected our App due to not compatible guidelines I cant figure out how to implement pay per user with InApp Purchase.

Because I cannot find a solution to increate the subscriptions because you can only have 1 Subscription per Account. I cant increase the subscription amount nor adjust prices of the subscription when they invite a user for example.

I really need help to figure out how to solve this type of issue. I appreciate any hints how I could solve this.