D?melo not D?melos-
Just a slight correction the phrase is d?melo and it carries the meaning of "what's up" when answering one's (cell) phone.
In the phone context:
This is language usage derived from the urban, pop/ hip hop culture in Latin street language which is quite popular among youth and a specific or select social group. Observe those who answer calls this way. It comes with the territory. Not specific to any one country but I will say I first noticed the usage in Panama City, Panama but that's not to to say it originated there. Most likely that's one of the places to where it spread.
I would find it hard to believe that people answer their home phone this way. This should not be confused with Diga or D?game, which you will definitely hear when one answers their phone at home. However, d?melo seems a bit odd or very "modern day" and certainly not the way the older crowd in the house would answer IMO.
One day, I decided to test the linguistic theory regarding certain "social groups". A friend of mine, a little older, who sticks to his own social group and social norms called me:
Phone rings:
LDG: D?melo
Mi amigo: No entiendo. ?Qu? significa eso?
...need I say more.
-LDG.