Complaint Procedure

Have now held on the phone for 49mins. This is the 17th call I have made this month, trying to get booking.com to give over MY money.Have not been able to send message on line . Have spoken to several different staff over the course of these 17 calls and they all say they will send email to finance ,who keep coming up with different excuses for not paying. Have been told earlier that booking.com do not have a proper complaint procedure. What to did next.