You can cancel at hotelkingdom.com. I believe they charge you approximately $10 to cancel, but you can do it (within the time period allowed, of course). Also, we have not been charged the entire amount at booking. We made a deposit, but not the whole hotel stay. I think there may be a few instances where they may ask you to pay in advance, but I think that is driven by a particular hotel or condo, not by hotelkingdom.com
Hope this helps.
By the way, I have canceled at hotelkingdom.com and was charged about $10.