Hi Hicham,
If your provider is Pearson VUE, then you can contact their customer support for rescheduling:
https://home.pearsonvue.com/microsoft/contact
In addition, you may want to ask your question in the Microsoft Certification forum using link below. There are support moderators over there that will respond to your question in 1 business day and can assist:
https://trainingsupport.microsoft.com/en-us/newthread?threadtype=Questions&forum=mcp
Please click Accept Answer if above was helpful.
Thanks.
-TP