Mobikwik — Promocode offered money back for 5 months but paid 3 months only

Address:

Krishna, Andhra Pradesh

Hi, I bought microsoft lumia 640 mobile in may 2015 while buyying this product flipkart, microsoft and mobikwik gave an offer 1000 cash back.i bought product by seeing this offers which i was attracted but later in the 4th month mobikwik saying that the offer is expired.so this is my complaint why they offered and later why they are saying this.my question is when they gave a promise and why did they are not obeying that promise. so please take neccessary action on this. thankyou.