Myflowerapp - Refund not received

I had ordered flowers for a friend's birthday from the online flower delivery website www.myflowerapp.com for Rs. **** on **th October ****. Around * PM that day they called me saying they can't deliver the flowers I asked but can deliver any cake, I refused for it and asked for a full refund. They called back saying that if they refund they will deduct **% of that amount as payment gateway transaction charges or can provide me a coupon for the amount I paid + **% which can be used on next purchase. I read very bad reviews online for them so asked for whatever amount they can refund back to my account. They informed that it will take * days but didn't get back any money. Finally I asked them to atleast provide the coupon, but didn't receive that as well. They have even stopped responding to my emails. I have come here as the last resort. Thanks!