Big Bazaar — they charged me for the bag separately

Address: 12A/37 W E A, Karol Bagh near Ashu Place Hotel, New Delhi, Delhi, 110005

Website: Big bazar

On 14th april 2019, monday, i bought things from big bazar, of above 2000/- and they charged me rupees 18 for the bag separately!!
I got to know today that you cannot be charged for the bag which contain there brand name written on it!!!
So my only complaint is how they charged me for the bag on which there brand name has been written 'bigbazar' has written.