Xiaomi India — refund not received mobile phone

Address:

Bangalore, Bangalore, Karnataka, 400092

I had placed an order for redmi note 7 pro. Product wasn't delivered and was taken back as replacement wasn't what they wanted.
I have been following up with then since many days. They are promising different date for refund everytime. And next time other executive apologises on previous one's behalf for lying. They are not even ready to take the complaint. They are lying every time i contact them.
What should i do?