Indraprastha Gas Limited [IGL] — Receiving estimated Gas bill.

We have received bill for March on 08.03.2023 and the due date is 29.03.2023
I contacted customer care because the amount of bill is more than the gas we have used.
Customer care member informed us that we are getting estimated bill for March month.
Why do we pay estimated bill, and not the actual bill?

I want you to provide us actual bills of each month and get the meter box checked.