Sounds like this problem:
SI B 12 13 08
Engine Electrical Systems
After Vehicle Repair, Service Engine Soon Lamp Cannot Be Switched Off
E90, E91, E92, E93 (3 Series)
E60, E61 (5 Series) all models equipped with M54, N52 and N52K engines
After a vehicle repair, the Service Engine Soon lamp cannot be switched
off. Fault code 2F9A (Ambient temp sensor, communication) is stored in
the DME and will not delete.
The Instrument Cluster needs a software reset.
Perform a software reset on the Instrument Cluster using the Instrument Cluster Test Functions
||Press and hold the trip reset button and turn on KL-R. Test Functions are shown in the upper liquid crystal display.
||Repeatedly press the trip reset button to reach test 19. Test 19.00 is displayed, together with Lock "ON", and Code "00".
||To unlock the Test Functions, repeatedly press the trip reset
button until the "Code" equals the sum of the last five digits of the
VIN (Vehicle Identification Number).
||Press the trip reset button to advance to Test # 21 for the S/W reset. Test 21 is displayed.
||Press the trip reset button to activate the S/W reset and extinguish the Service Engine Soon lamp.
Maybe they have to do this again, and they screwed it up the first time?
You might also try another dealer.
Or you might demand an appointment with a Field Technician, who will visit the dealer and work this out properly.