No Feedback and really bad service

My name is Thando and I bought a phone on a Saturday 29th of august and on Tuesday the 1st of September 3 days later the phone started having problems like freezing and switching off in the middle of a running application, i then returned it back to the shop on Friday the 4th i was told they will take it in for repairs because it has passed the 7 day period and the process will take another 7 days for them to return it back to me, and they will call me to come fetch the phone. The 1st week passed without any feedback so i called them at Foschini to enquire but i was told the people handling phones were not available, a second and third week passed without any feedback.. this is the fourth week without any feedback. i then called today morning and i was told they don't know whom i bought the phone with. they refused to give me a refund nor another phone i really don't know what to do. please help!!