Hi Alejandro Montenegro Ortiz,
Thank you for reaching out to us on the Microsoft Q&A forum.
To address your issue with switching back to the Developer subscription for your Microsoft Azure Sponsorship Subscription, please open a support ticket with the Founders Hub support team by following these steps: https://foundershub.startups.microsoft.com/signup?drawer_open=true please click on "Support" on this page to submit support ticket.
Please reach out to us if you have any other queries.
If the information is helpful, please Accept Answer & Upvote so that it would be helpful to other community members.