I've recently bought a C-Class (w204)and in the armrest it's got this set up;
I'm pretty sure it's and old style mobile phone attachment so the answer to the first two questions are no and no, if I'm right would much appreciate help with the third please!
Yes, fairly sure it's the 'preparation for phone' or whatever it was called, an option IIRC. No idea how to remove it, sorry. Is it not shown in the handbook, if so, might be more obvious how to disconnect it.