Pepperfry.com - Incorrect item delivered

I had ordered a kingsize mattress from pepperfry which got delivered on the **th of August. The mattress sent was of an incorrect size. I raised a return immediately and was assured by the customer support team that the item will be picked up within a couple of days and a return will be initiated. I have been following up with them continuously since then and they have stopped replying to my emails and calls too. That chat agents just give stupid replies like” The case manager has left the company” hence there is a delay in refund and pickup. Im tired of this and haven’t gotten any resolution. I have emailed their grievance officer multiple times too but my complaint hasn’t been addressed yet. The chat agents just say a manager will callback but no one has called me in the last ** days.