I have a 2016 GLA on order and expect to be deliverd the 15th of june.Jan, I think it depends on what year you have. The 2015 GLA for the USA has the Becker Map Pilot, which also has a provision for an SD card. I think that the 2016 model has a different system in it and has the SD card slot on the dash. I just purchased the Becker unit and am learning how to use it.
I also think that both systems have to be pre-wired from the factory in order for these factory systems to work. Of course you can always purchase an aftermarket unit in place of the factory items.
Also do a search as there more info on the systems here on the forum.