Priceline complaint: Overcharged, overpaid for seats I did not receive

I paid way over the price the actual airline offered come to find out after booking with Priceline. The main issue I have is that I paid EXTRA for seats because I have a serious knee injury and when I arrived to the airport I was informed that Priceline never communicated the seat request to the airline and I ended up being put in a very uncomfortable position for a 22 hour flight. I paid 7.444.00 dollars for seats that were about 1200 dollar seats. I am so upset I was taken advantage of and the Priceline acts like they hold no responsibility for this when they collected the money, overcharged me, and took MORE MONEY on top of the overpaid ticket cost for seats they didn’t even let the airline know they took money for. This is fraudulent behavior and they should not be able to do this to people, . I will Never ever use Priceline again and will let everyone know not to use them. I feel they should refund some of my money back.