Want to complaint in consumer court but don't know how it works

I and my family members won a coupon code from magicpin Application by playing their play and win contest.

The coupon is to get discount at restaurant listed under the offer.

Coupon is showing in my app when I won it and it was there yesterday too.

So me and my family members went to a restaurant 12 kms aways from my home .

Upon reaching the restaurant I realised that none of our apps showing the coupon code that was available till yesterday.

I contacted customer care through their chat option but instead of answering and solving my problem they kept asking multiple questions which I answered too.

Asked for coupon code and title with screenshot and thankfully I have it.

( Normally people don't screenshot each and every coupon code they get )

I answered everything and when I opened the app again to check the coupon code showed as claimed.

I asked CC to give me details where I have used the coupon give me date , time , place and bill etc and they said there is no recent transaction showing for my account.

I have to return to home without eating with my family members and have to face humiliation and mental stress due to this incident.

Customer care failed to resolve it and keep asking same question again and again.

I want to file a complain but don't know how to do it.

Please help.