i wouldnt let the dealer touch my car to locate rattles - not after the damage they have caused just trying to reverse it off the work lift (twice its been on their ramp, twice its come back damaged)
i had/have issues with rattles and most of which i cured myself by removing the trim and sticking on some felt tape, spraying parts with silicon lube etc or simply refitting the panel correctly.
the worst rattle on my car was the centre console. i found a good few areas it does it in and ways to cure it
apply felt tape to the areas where the arm rest close down onto. the arm rest bounces around a lot.
make sure seat belt bucks arent touching the centre console. this happens if your tall like me and the seat is far back.
the handbrake gater rattles like hell (its a roller blind type thing inside a track which moves up and down with the handbrake. some felt tape on the tracks sorts it right out BUT its a nightmare to access. the whole centre console need to be stripped out to get to it).
to do this you remove the cup holders at the back, remove MDI input, remove screw under front bottle opener/cup holder and pull it out.
my car had this rattle and would come in exactly 3100rpm and go at 3500rpm. very annoying on motorways

also the handbrake rattles against the centre console when its down (off). some felt tape on the are where the handbrake touches the centre console sorts it.
i did this fix the day after i bought the car brand new.
others i have fixed are;
sunglasses holder/light switch area
drivers and passenger B pilar - put a torn up car wash sponge in there.
back seats rattle. gaffer tape on the hooks then locking the seats back sorts it.
drivers side door trim (main one fixed but the electric mirror switch still rattles as its a separate moulding to window switch and rattles inside it)
still need to fix passenger side floor/door/seat area rattle but its impossible to find as i cant reach it from drivers seat and it stops when someone sits in the seat.