Zomato — worst food order service experience. cheated on the name of discount 1st order

So i have order food online forever on multiple apps. But then i tried using zomato for the first time for a restaurant which wasn't serving any other app. On the home page, it showed that the first 5 orders of mine will have a 50% discount. So i signed up and placed the order using the promo code wherein the revised billing amount was shown with 50% less on the total. Hence, i went ahead and placed the order. Later when i checked, the entire amount on the bill had been deducted from my account. So i tried cancelling the order on the web but they don't have an option for it. So i called the customer care multiple times where it goes waiting for over 10 minutes and later says no one's available to take the call. So i register a complaint on their website again in vain.
After having used at least 6 other food ordering apps, including the really local ones, this has been my worst experience. They lure the customers with fake offers and have no care in the name of customer care. There's no way you can reach them once the money is deducted. # service. Don't recommend them to anyone.