Hi Jorge Antonio Ruiz esparza Galván ,
Welcome to Microsoft Q&A Forum, thank you for posting your query here!
Microsoft Certification / Exams is currently not supported in the Q&A forums.
Maybe one of the links is helpful:
Microsoft Training & Certification is supported on their own forums:
Microsoft Training Support Forum
Microsoft Certification - Exam Registration/Scheduling
Microsoft Certification - Profile/MCID Assistance
It's possible to ask questions by clicking on "Get Started" -> "Ask a Question" or "Ask a new question >" and Learn/Cert Moderators will help you.
Pearson VUE Support:
Pearson VUE - Customer Service
For more information:
https://trainingsupport.microsoft.com/en-us/mcp/forum/all/how-can-i-reschedule-my-az-900-exam/aef06135-89d4-4a1d-afad-fabd167048ce
https://learn.microsoft.com/en-us/credentials/support/reschedule-and-cancellation-policy
If you have any other questions or are still running into more issues, let me know in the "comments" and I would be happy to help you,
Please do not forget to "Accept the answer” and “up-vote” wherever the information provided helps you, this can be beneficial to other community members.