Show your dealer the 2003 model year overview at Mercedes-Benz, Home of Mercedes-Benz Luxury Automobiles
- the MBUSA site. Note that "Pneumatic door and trunk closing assist" are listed as standard features and are not identified among an option package. You should have the feature.
You may also have, in your original paperwork - the records from the purchase of your car - the original window sticker. It will list standard equipment. I have seen some dealers include it in the owners manual package.
Your dealer has told you the kind of thing my former dealer in Baltimore often told me, to discover (through these forums) that he was wrong and the feature was simply in need of reset or repair. Among them that I can specifically recall, automatic steering wheel repositioning, automatic 3-flashing of the lane change signal, key matching to driver preferences, and the ability to lower/raise all windows while unlocking or locking the car.
For each and every one, I was told it was a feature that was either optional, or that came out in a subsequent model. It was all BS.
I have found wide variance in the knowledge of "service writers." The techs who do the actual work know far more, unless the "service writer" had first been a tech in Mercedes and had fairly recent experience, which is not always the case.
In two of the cases above, a tech came out and fixed the problem on the spot, explained how to handle it myself if it happened again (specifically, the steering wheel height and key matching; the others needed repair). A tech also pointed out what to look for in developing Airmatic leaks at the top of the strut mounts and several other things I have shared on the forum. It's what got me started on the forums in the first place.
It's also what convinced me to research a problem before bringing the car in to start with. Tends to disarm the BSer immediately.
I would deal with a different service writer - even if he was "assigned" to you as part of a team. I would ask to speak directly to the tech who would work the problem. And, if that failed, I would ask to speak to the manager of the entire service department (not the service writer). At least in my experience they were fairly knowledgeable, and if not, would call the proper tech.
Sometimes I believe the service writers think you're too stupid to understand your car, or too busy to care, and they blow you off. I think the techs, once you get to them, are proud of their knowledge and know if you went that far, you want an answer. The ones I have dealt with have actually been happy to share their knowledge, and talk to someone interested enough to listen.
Do that, and they'll know you stayed at a Holiday Inn Express the night before.