Uber India — Free ride not given

I booked Uber cab under free ride scheme on[protected].
Total fare was 298/-
I had a free ride worth 300/- in my a/c.
But they refused to give me free ride.
I had to pay the discounted amount 258/-.
I contacted Uber 12 times till now, but no reply has come.
I wrote to their grievance email ID as well, but they also did not reply.
If they don't want to give free rides, then why do they offer them?
I request all to stop using Cheater company like Uber.
Thank you.