For example, it subscribes the user to a plan that charges $100 every month.
But I have to change the price and now charge $150 every month.
But Stripe tells me that since I already have active users with that price, it can´t be changed.
How can I change the price for both, existing users and for new users.
I would probably move all your users to a new plan prorated if you can’t change it directly via Stripe. Or read this, I just did a Google search and this was one of the articles that popped up. It may have a solution?