spoken english

[akbar]

recently when i tried a number it was wrong number! voice on other side said ,''who is calling to?''
this one is correct? i think whom you are calling to? is correct. or in spoken english who is calling to is also right?

[Casiopea]

In North America, it'd be,

"Who are you calling?"
"Who are you looking for?"
"Who are you trying to call?"
"Who is the call for?"
"Who is the call to?"

"Who is calling to?" is not North American English.