Paytm — didn't receive cash back and customer care service is not responding

Address:	New Delhi, Delhi, 110021
Website:	Paytm mall

I have purchased a samsung s9 plus from paytm for rs -64900 on 15th march. It promised to give a cashback of 6000 withing 24 hours but i didn't get it till now. I am trying to reach paytm daily but it is not replying. I have tried calling coustomer care several times, waited for 10-15 minutes but there no human voice. Now i am confused what to do as my 6000 cashback is still lingering in air.