Mobikwik - Charged 399 for Activation without any prior notice and also didn t receive any cashback that I was

I placed an order on Zomato on Dec **, **** at *.**PM of ₹*** via Mobikwik Zip Pay Later because they were giving cashback upto ₹***. After about two weeks they sent me message stating that I have to pay ₹***(*** Zomato Order+*** Activation Fee) which includes their activation fee. I was very angry at this moment because I was completely unaware that I would be charged such a big amount for using Mobikwik's pay later service. No other pay later services that I've used so far asked for any kind of Activation Fee except Mobikwik. I thought of not paying at first but they persistently called my number, sent messages, emails and everything for *-* days, until finally I paid ₹*** on Tue Dec ** ****, at *.** AM. I was forced to pay the amount because they stated to charge ₹**** extra for late payment. I also didn't receive any kind of cashback that I was supposed to get from my Zomato Order. After all this, I contacted them to close my account after knowing that they charge ₹***-*** as maintenance fee per year. But even after *-* tries they're not replying to my grievance. I was lured into using Mobikwik's Pay later option because of fancy cashback offers(which I never received) and then they charged another ₹*** in the name of Activation Fee. Please help me get my money back and also get justice for such fraudulent by such a big Banking company.