Any point in complaining

had an account with pp for over 10 years not regular customer but certainly not a winner over that time. Backed the second in the norfolk today as they were offering money back as a free bet if horse finishes 2nd or 3rd. Have now been told they will not honour this as a traders decision has been taken not to offer this to me. They had not forwarned me and so i was completely unaware of this. can this be right and is there any point in taking it further?. in which case who to ?