Bharat Sanchar Nigam [BSNL] — unable to pay bill before due date

Address:

East Godavari, Andhra Pradesh, 533308

I was trying to pay the bill but not allowing as the due date has already passed.
Since one year, due date was 28th of month but this time it's 24th.
Previously, it's acceptable even though i pay the bill beyond due date,
But why it's not happening this time?

Kindly allow me to pay bill so that i can access & re-use internet.
Phone :[protected]