worst nightmare

i booked for me and my friend for a few days at park central rosebank (24th-26th june)and my bank account was debited and I cancelled the booking within 24 hours of booking and i was refunded and booking.com debited R2000 from my bank account for no reason and now my bank account is on a minus because of them,i want my money as i cancelled the booking within 24 hours and i dont know what the R2000 is for..the booking was for Portia Madihlaba