3 Bedroom apartment for a 2bedroom at afri ski

I am not happy with the service i have been receiving from booking.com, i booked an apartment through booking.com which had 3 bedrooms only to get to the property and we were given 2 bedrooms. I have been calling booking.com for my refund and all im getting is they need proof that we were given 2 bedrooms, that time we did not take any pictures and we believe its their duty to call the property and ask them how many rooms they offered us, im so dissapointed that instead of booking.com to take accountability they want me to investigate the matter on their behalf. Be aware as you book from booking.com that whatever specifications are on the adverti*****t are as the property says they are.