sim swop

I requested cell c to do a sim swop for me on 27 Jan 2016 and they promised to call me back in 4hrs. They only got back to me 48hrs later and we according to my knowledge processed the sim swop only to find that they used a wrong seriel number. they want me to pay for another sim swop saying its their word against mine. Why do they records their calls if they are too lazy to go bqck to the recorded call to verify whose fault it was. The cell phone number in questiob is ***.