Cell phone

I bought a cell phone at one of your shops using my account and the phone is giving me a problems, I tried to return it and the store is closed what must I do now. I went to a nearest shop in Elof Jozi they tried to assist but with no luck, I have lost my slip but I am still paying for this phone and it's not working and I can not take it back tell me what must I do must I pay for something that I am not able to use and please don't sell that type of cell phone to people as it's a bad from and problematic please tell me what must I do sins the shop is closed and I can not get my slip and I have a account with you