Payment and purchase system for Nextcloud

Hi.

Does anyone know of a system that integrates with NextCloud or a Dashboard, I would like to sell hosting services or improvements in the amount of storage with NextCloud, but I can’t find any information to carry out this?

Thank you in advance for your responses.

You mean, that you create a user profile and assign an amount of storage to it and sell this?
Or, that the buyer gets their own instance?

That the user can create an account and that when creating their account the user has a section in case they want more storage, pay for more storage, just like Mediafire, Mega or any paid cloud with a free service works.