Hey there, Prince Kumar
According to this support article (https://learn.microsoft.com/en-us/azure/cost-management-billing/manage/cancel-azure-subscription), if you have cancelled your subscription by accident, you should contact support within 90 days of the subscription being cancelled.
Please can you reach out to support request using this link: https://portal.azure.com/#view/Microsoft_Azure_Support/HelpAndSupportBlade/%7E/overview
Thanks,
Nathan