Booking.com / TAAG airlines

Hi, bought some air tickets from Bookiing.com in September at 12K each to travel end November and paid an extra R1300 per ticket to be able to change dates once without penalties. Due to serious health issues with family member overseas I tried to bring forward the departure date and they, booking.com want to charge me 13k per ticket extra to change the dates which is more than the original price of ticket. Here`s the Stink : I went onto the airlines web page and fresh tickets for my required dates only cost 2k more...