Hello Jitender Kumar,
Thank you for posting your question in the Microsoft Community Q&A.
I understand that you would like to know how to get refund on charges in Azure.
To start with, did you upgrade your subscription to pay-as-you-go as you wont be charged for using a free subscription. You will only be charged when you manually upgrade your subscription to pay-as-you-go subscription.
You can create a new support ticket within your tenant to the billing Team to get more information.
let me know if further assistance is required.
Babafemi