Karthika Sarees - Refused to take back the item after agreeing to do so.

Mosquito net not as per requirement.
Hello Sir/Madam,
I purchased Mosquito Net from Karthika #****, Karthika Building, Ganapat Gali, Belgaum, Telephone: ****-*******, Receipt #: P*****, on September *, ****. While purchasing, I asked their salesperson to open the net completely and show me. He insisted that everything is alright and there is no need to open it and if there is some problem or defect, I can bring it back. I reminded him that as per shop’s policy, goods once sold cannot be taken back or exchanged. He assured me that he will be handling this particular counter and I can approach him if there is any fault in the product and I purchased that mosquito net. After returning home and checking the net, I found that it was partitioned one and not full net making it worthless as mosquitoes can enter through the slit. Next day, i.e. on September *, ****, I tried to return the net, but that particular salesperson was not on the counter and the other salesperson said I can exchange the net for some other article and won’t get cash back. At least he agreed that it was their fault but asked me to come on Tuesday, i.e. September *, ****, as they settle such matters on Tuesdays.
On Tuesday, the shop was closed, i.e. that salesman bluffed and this caused me loss of time and money. Today, i.e. on September *, ****, I approached them again and this time the manager agreed to return money, and the salesman tore the bill but suddenly started arguing with me that I had used the said product which was not the case.
First, it was their fault that they did not open the net to show me and, moreover, now they were checking the net after opening it, see the irony of the fact.
By now, the manager and salesman decided not to return the money and asked me to leave along with the product as I had used it. I said I will complain and asked for the bill which the salesman had torn off. Now, he brought different bill with different Invoice number and I asked him to give me the same bill which he did manage but with different date, i.e. September *, ****.
This was how I was cheated. Kindly look into this matter urgently.

Thank you