Reservation few months earlier

Please can you help me? 
I put my apartment here but somebody reserve first day New Years eve 

I didnt now that it is possible 

i dont want rent apartment per that price because now is Avgust and 5 times will be increase till the 31 th December


please help me thay can rent my apartment to third  

 Persons .. he reserve for 200 euros and price for 5 night will be 1000 e 

please help me

i req cancellation but he want to call you