Some dealers provide the "free" oil changes if you go by their, the dealer's, service schedule - which usually does everything far sooner than owner's manual recommended. Is is "wrong"? Well...not really. Better question is if it is necessary.
I would ask around and try to find a local, independent repair garage to bring your truck to. If you get good, honest mechanics, it will pay you back a lot to have them do work on your truck. When I can't do it, I pay a local garage the $35 for an oil change - and they usually give a list of things I should think about doing, but they never push work unless it is a true emergency (they are way too busy as it is).