Payment

Hi, 

I would like to ask, what to do if guest didnt pay for a stay? I found out late that I didnt set up booking.com payment system, all the time i thought that its already set up coz I filled up my bank details so I thought its done right away, and now I found out that already two guests stayed in my accomodation and left without a word.

Is there anythin Booking.com can do about it, or do I need conctact the guest directly or just to contact police?

Thanks for a help..