SIM CARD NOT WORKING

I bought the cell phone for my sister at Pepcell at Midrand Boulders Mall last week(20 January 2015). The sim card was reca ed and upon arrival at home the phone never worked. We bought the phone as it came with 100Mb of data for 12 months. the number is ***. when we took the phone back, we were told that it is/was not their fault. It is the fault of MTN, when we requested for our money to be returned., we were told that they will not be able to return our money.