Paytm Mall - Package not picked up for exchange

I ordered Oppo F** pro on Paytm mall since it had an amazing exchange offer. They give **** exchange bonus along with the exchange product price (say my old phone Redmi Note * exchange value was **** and along with the exchange bonus its value was around ****). The reason I went on to this product is because of this exchange offer. Exchange should have been picked by within ** hours from the delivery of the product. I have been calling them from ** hours of the delivery asking for exchange pickup. Every time I call they give a timeline of max * days. It's been ** days now. I have called them several times. The issue even got escalated and I spoke to some higher official. After ** days of continuous efforts, I get a mail from Paytm Mall stating that "Sorry! The exchange pickup was unsuccessful because it did not meet the exchange criteria. We will not be able to process your exchange cashback. Read the terms and conditions for more information on rejection."
Without even making an effort to call me for pickup and checking the product they have sent this email to me. I immediately called customer care and they say "no such mail was sent from our side" but I have proof of that mail in my Inbox. They still ask for some time to resolve this issue and it's going on without an end. **** of my money is stuck. They are fooling people with such fake exchange policies. I am ready to face the court and get back my money.