Part of the Taillight missing

Hi<br> <br> The experience that my son and I have had at Renault Bryanston (in William Nicol drive) has been very poor. Last year (30 June 2015) we took the car in for a service and a few days later we noticed that a piece of the left back taillight was missing (black beading had fallen off) - it had probably fallen off during driving. We went to Renault Bryanston to ask for them to identify the problem and they were quite surprised to see what had happened especially because they were convinced that the taillight and beading was one part. When we asked them to replace it they said that we had to a pay because it was not under warranty (the car was only 6 months old at the time of the service). Months have gone by and in January 2016 I spoke to the service manager, Christopher, who said it was very strange and that he will help us, only to be told 4 weeks later that again they can do nothing for us and that we need to pay for the part, I would like to remind you it is supposed to be one part joined to the tail light (according to Renault). We would like Renault to do the responsible thing and replace the faulty part and adhere to the warranty that they give their cars.