Well technically i didn't ask to get it done, i asked how to do it.
I got given an answer that wasn't exactly what i was looking for but nevermind that, it's only a point of detail.

If i ask custommer support to convert USD to EUR on my account, this would be done? How come there isn't a possibility for me to do it myself, or eventually, as on Bitstamp, to get USD converted and send to my account?

Idea is to get to know exactly how much of each i'm exchanging.
Somehting like :
"amount to convert: USD 100
Amount converted :  €75
Click here to proceed"

No fees would be best of course