Seats given away??????

My Son and his Fianc? (Pregnant - 6 months) had tickets to travel from Potchefstroom to Winterton this morning and received a call 10 minutes before they were meant to board at 11h00 to be informed that they have given their seats away but that they can wait for the next coach at 20h00. My children are from Sasolburg (just over an hour away from Potch). I am on route home from Harrismith and am absolutely furious. Friends of mine travelled through to Winterton with my kids (what a way for another family to have to spend Good Friday - Travelling 6 hours!! I am ever so grateful to them). How could this have happened!!! I would like some answers and refund for the trip!