Fab Hotels — invoice with less amount

I booked fab nest hotel (Koramangala - bangalore) from 15th oct to 20oct) and paid a amount of 8999.95 as per their charges, but i vacated the hotel on 19th and as i did not informed them before 24 hrs, i did not get the refund of one day. But surprisingly i received a invoice only for rs 7199.85, when i ask the customer support, they told, their software not supporting the full invoice, so they can not provide the same
But i need a invoice for the amount i paid, that is 8999.95
I tried to contact them multiple times, but there is no response from them.