Sterns Gillwell mall bad service

On the 7th of May I bought A new phone. ON the 8th i returned it bcos ir was switching it selfnon and off. Instead of them to give me a new phone or money back they sent that phone for repair. It came back with the same problem. Now they want me to take back that phone which has probl they dont want to give me my money back. They got bad approach when i want my money back or a new phone.