Already sent it in to the distributor today. Since they accepted it, I'm guessing the wrong cabling isn't DAViS' fault. I'll definitely let the dealer have a piece of my mind regarding this issue.
But as per the distributor, it can only be settled after the unit returns from the service centre in Singapore. So until then, I still don't have what I've paid for.

On a side note, went to Cap Square for lunch today, and I realised that there was a Sennheiser shop there. Dropped by and saw that the MX400s they had in stock had:
- a symmetrical cable setup
- had the model number printed on the side of both earbuds (which mine didnt have)
- the 3.5mm jack was silver in colour (the one I received was gold)

All those details almost match exactly what my old pair of MX500 had. The best part is, it was on sale for only RM59  .
Whats even more interesting was, the shopkeeper said that they stock their goods from the distributor that DAViS referred me to....

So I'm guessing that this confusion would only be settled once the earphones are back from Singapore.