Blatant overcharging

Eight of us booked a flight to Dubrovnik in February and paid in February. My daughter has to re write an exam she failed and we have to change the flight dates for one ticket. I Googled tickets now and got prices ranging from R16 000 to +/-R17500 booking now. The airlines have had our money since February, now you guys are going to charge us R22868? I think it is a ******* and will tell everyone I know.