"Booking.com" is an on-line reservation service owned by Priceline but it is not the same as Priceline's booking agency, so any issues relate to the site on which the reservation was made and the hotel. The site operates out of the Netherlands, whereas Priceline's epomymous travel sites are based in the US.
When using that site, the reservation clearly indicates the "max persons" for the room.
Here is the information from booking.com's web page:
Booking.com bv
Weteringschans 28-4
1017 SG Amsterdam
Netherlands
CEO:
C.P.H.M. Koolen, CEO
Contact information:
Tel: +31 20 712 5600
Fax: +31 20 712 5609
Email:
[email protected]
Good luck.