You can follow the below to know your charges in detail.
Method 1:
Step 1: Download your bill from Airtel Thanks for Business. It is in PDF format
Step 2: When you open the bill, you can find the breakup of charges on the first page. In the subsequent pages, you can find the charge details of your entire account including your plan details, monthly charges, usage charges and any one time charges.
Method 2:
Incase if you wish to get an Itemized Bill, which has call wise usage detail like duration and charges, you can go to the Itemized Bill section on the Billing Dashboard and download your Itemized Bill