Royal Enfield - Faulty bike

I had purchased new Royal Enfield Classic *** in the month of June ****, after a while I found that the bike has a issue of running off. I mentioned this issue in my first service, but it was not resolved. I had same same issue again and decided to visit Royal Enfield Service Center (Karnavati Bikes Ahmedabad) and I was told that the bike will be kept for SOP (Standard Operating Procedure) for * days. I agreed and kept the bike there, instead of * days they ask me to keep the vehicle for one day, this continued and now the scenario is that the bike is at service center since ** days and they are stating that the issue has been resolved, I asked them to provide me this resolution in writing but they refuse. They know that the bike is faulty. My goal is to have money back or the company should replace this faulty bike.