No Answer to my query - Lack of integrity??

My dealer has now decided to set the computer to make service intervals every 15,000 Km or 1 year. The excuse offered is that the oils available nowadays are inferior. Really? Do I need to direct my complaint to Oil companies? I need a written response, so that I can take this further. So I logged an email query on Peugeot South Africa's web site. I was informed that I will be contacted in 48 hours. That was a week ago. I have logged further queries, to no avail. What is the problem? It is a **** to force more business for the dealerships ? Does Peugeot South Africa actually support this???