Paytm — Paytm cashback not came

Address:

Pune, Maharashtra

I had bought a mobile phone i.e microsoft lumia 535 (black) with order no.[protected] four to five days back and it has been delivered but i haven't got the cashback. The actual cost of the phone is 8747 and if customer buys this product then there will be a cashback of 20% i.e 1749 using promocode GET20. Please check this let me know why it has not been send.