Support for external memory cards is on the wish list but hasn't been implemented for over a year now:

http://www.mediamonkey.com/forum/viewtopic.php?t=15180&highlight=phone+card

Unfortunately, as more and more users switch from a stand alone mp3 player to the one integrated in a cell phone.

... and it's not listed in the devices either, although I can easily access it through explorer.

Any reason why I can't get MM to see the MicroSD card in my Nokia N82?