Zomato - Cheating with customers

January ** ,****
I ordered food from Zomato (Order Number- **********). I ordered food because I was having Zomato credits which I want to redeem on my order.
During the checkout, there was no option for selecting Zomato credits as a mode of payment. I recollected that the customer support executive told me during credits giving that I can use these credits on any upcoming order. There was no promo code given for that, so I thought it would be automatically applied.
So, I placed my order. Even to confirm, I without any further delay contacted the customer support to verify the aforementioned.
And then to my surprise, customer executive told me that you can't use credits or any discount coupon on a COD order.
But I have used a discount coupon (TASTY) which worked on COD order and when I mentioned that to customer support, they said that it is a technical error.
So, firstly it proves that your system is pathetic.
I asked for where it is written in your Terms that a credit can't be used with a COD order, or have you informed me while giving. To which the Customer support sent me the terms, and I read that to finally conclude that there is nothing such mentioned.
The Customer support became impatient and just apologised.
I asked him again to cancel the order, else I won't receive it, to which they said that if so then they will block me from COD and promotional offers.
How can you guys behave so bad with customers?
They said you will receive an email for your query, for which I'm still waiting.
Then I went to twitter for help, to which these guys are blatantly ignoring me.
You guys really lack in customer service. You guys are the real demons.