Hello @BENMEZIANE Hatim ,
Welcome to Microsoft Q&A Platform. Thank you for reaching out & hope you are doing well.
As mentioned in the FAQ section of Azure DDOS Protection pricing page, if your DDoS Protection service is active for the entire month, you will be charged the monthly fee regardless of usage. However, if your service was active only for a portion of the month, you would only receive a prorated bill for the hours used and data transfer overage incurred.
Kindly let us know if the above helps or you need further assistance on this issue.
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