W204 C180 Executive SE 2013 Automatic / COMAND NTG4.7 and Morel speakers fitted by www.comand.co.uk
Maps updates for COMAND navigation are carried-out by downloading the maps to a USB stick or SD-Card, then uploading it into the internal hard disk drive in the car.
Maps updates for Garmin Map Pilot on Audio20 are carried-out by purchasing the software and maps together a new SD-Card. The Audio20 does not have an internal hard disk drive, instead the Navigation software and the maps remain on the SD-card and run from there.
So the first thing to do is check whether you have COMAND Navigation, or Garmin Map Pilot on Audio20?
When the car starts, does the message on the screen say 'Don't let COMAND distract you...' or 'Don't let the system distract you...'?
If the former, you have COMANdD. If the latter, you have Audio20.
Also, in either case you can also update the firmware, i.e. the software on the unit itself (not the maps data), but this needs to be done by the dealer. The new firmware itself is free, but the dealer will charge for labour based on how long it takes.