Flying Machine — fraud against offer and bill amount

Address:

New Delhi, Delhi, FMJK0573

V3s mall, laxmi nagar, new delhi
On 21 nov 2018, an offer was going on, on purchase of 6000, 1000 off, so i bought one jacket and one t-shirt worth total 6000 and i was pay 5000, on the very next day, i exchange with the same brand 1 jacket which is worth 6000, then the owner of that outlet said the offer is not valid on exchange and i will pay 1000 more.
They have given me non-computerized bill and said their printer is not working.
I only want you to compensate me and take necessary action against the manager or owner whatever he is, for committing fraud against me as well as company policy, by putting down the excess 1000 in their pocket.
Please take action against them and returned my money, otherwise i am going to file fir against flying machine.
Here i am also attaching the bill.
Hoping for quick and positive response
Thanks.