Hi Noemie,
Thank you for contacting the Microsoft Community.
I completely understand how important it is for you to be able to update your legal name accurately on your profile for your scheduled exam. Please be assured that I'm committed to assist you with this.
As it is crucial to have your complete Legal Name, to move forward with your request, I have started a private message thread where you can provide the necessary details. This will allow me to locate and verify your profile completely, so I can review and process your legal name change request accordingly.
You can access our private message by clicking the following link: Private Messages - Microsoft Community

If you need immediate assistance with your exam, please contact Pearson Vue Support. They have the necessary information about your appointment and can help with rescheduling options and other recommendations while we are still processing your legal name change request.
Thank you in advance for your cooperation.
I look forward to your response. Please note that if no response is received after two business days, the case will be closed and locked. After the case is locked, we will no longer be able to respond, even through Private Messages.
Best regards,