Uber Eats India - Discount Coupon Not Applied and Cancellation Denied

I placed an order through uber eats for Subway and applied the coupon code **SUBWAY, however the discount did not apply on my order after i placed the order, so i called the customer service within * minute of placing the order to cancel the order, they pretended to call the subway outlet and then told me that the vendor was not picking up the order and that i will have to pay for the order and cannot cancel. They have done this to me before and i had to pay the full invoice amount even though i cancelled the order. I have lost more than *** rupees because of this cheating.