reschedule my exam

You don't provide enough information. No one here has access to the systems so candidate id etc is of no use. You can only reschedule with more than 24 hours before your exam. If you have issues taking the exam you should contact the exam provider's support. You reference a case number, if you already have a case open with Pearson Vue, you need to wait for them to finish their investigation

To reschedule the PL-300 exam, use the standard Microsoft certification reschedule process. The case number and IDs provided are not needed for the basic reschedule steps.

Follow these steps:

1. Go to the certification dashboard and sign in with the same account used to schedule the exam.
2. Locate the existing PL-300 exam appointment.
3. Choose the option to Reschedule (or Cancel if needed) and follow the prompts. This will redirect to Pearson VUE to pick a new date/time.
4. Confirm the new appointment.

Important policy points:

• Exams must be rescheduled or cancelled at least 24 hours before the appointment. If cancelled or rescheduled with less than 24 hours’ notice, the entire exam fee is forfeited.
• For free exam offers (for example, from a Cloud Skills Challenge), rescheduling must occur before the offer expiration date; otherwise, the free offer may be forfeited.
• If there are issues rescheduling online, contact Pearson VUE support or Microsoft Certification Support as indicated in the documentation.

For detailed policy and step-by-step guidance, see the referenced articles.

References:

• Register and schedule an exam
• An Important Update on Microsoft Training and Certification
• Microsoft Ignite Cloud Skills Challenge – November 2021: Free Certification Exam
• Microsoft Build Cloud Skills Challenge 2020: Free Certification Exam
• Microsoft Build Cloud Skills Challenge May 2022: Free Certification Exam
• How to reschedule the exam - Microsoft Q&A