Bajaj finserv - False promises qnd fraud by Bajaj Customer service

I have cancelled my order of mobile with Bajaj market. And ordered another mobile with Samsung shop. But the order wasn't cancelled by BAJAJ due to their lazy customer service and was delivered to me. I received the cancelled order as the pack was similar with my actual order( whose delivery date was also same day i.e. ** October ****). I immediately contacted Bajaj and asked them whether they can take back their product or not?? The customer service assured and promised me on ** October **** that within ** hours they will take their product back and asked me not to open the delivered order. Since they assured me, so I accepted my original order the next day. After I accepted both the orders.
They took a sharp U turn. They started the loan of both the orders immediately ( which also contains the cancelled order) and when I again contacted them, they told "sorry it cannot be returned as the product is delivered". I have recordings of my raised query and their fake promises both.
The basic issue is that if they were not capable to take back their delivered product then why they did fake promise and gave me false assurance. I wasn't forcing them to do so. If they would not have promised, I would have cancelled the other order. But since they promised to take it back so I received my actual order.
Now I want that they should immediately take back their packed and sealed product as per the promise made by them and refund my amount.
I have raised this issue many times with them but they are just delaying it so that my EMIs start and once they start I would be liable to pay them.
This is clear case of fraud with me as a customer by Bajaj customer service