Complaint regarding AJIO NORETURN100 coupon

I have placed the order in AJIO with out applying any coupon code manually. But a coupon called “NORETURN100” is being applied by default and then when we try to return the product, they’re saying that it cannot be returned because we had applied the coupon, but they applied it and without informing us. Backend applying the coupon code and make the customers should take the product. And i have faced the issue that i had paid the total amount while placed the order but in the app it was showing not paid . i had discussed with the customer care and they were keep on saying sorry for the  inconvenience, we can’t help you on this issue. Please take the action on AJIO by doing these activities