Hi JAYI SRIHARI ,
Most likely one month free trial might have expired for you. You can use all the services for a Month and after that you will have to convert subscription to pay-as-you-go. In this case, you will be charged based on the service usage.
You can also explore Azure for student subscription
Reference - https://azure.microsoft.com/en-in/free/free-account-students-faq/ https://azure.microsoft.com/en-in/free/students/
You can also use Microsoft learn where access is given to portal for specific hands-on task https://learn.microsoft.com/en-us/learn/
Hope it helps.