Twin earth wire

I went to builders in Bedworth park I was buying a twin earth wire 100mm which was R600 but when I went to the till to pay I was charge R1500. I was told it's was a mistake from the head office than called the head office I got 100% poor service from the head office of builders and that promotion is over. I am still waiting for they're call since from 4 November 2023 till today no call from the.