consultant's error, cost me

my little sister went to shoprite to buy a bus tickets, one from Mokopane to Johannesburg and then another one, from Johannesburg to Bloemfontein. this was both for the 27 March, so she informed the lady there that she need two bus tickets and informed her more than twice that it was for that sunday but she still sold her one ticket for the 27 March and another for the 24 March. so a day later when were confirming the times for bus, we noticed that the one date was incorrect, and we took it back and were told that, we needed to buy another one because the matter will take 7 days to be corrected by computicket. until today, we have not been refunded.