If it has a +1 52 prefix before the area code then is some of those people trying to blackmail on you, the 555 area code is for mexico city and the +1 52 indicates this call is coming from them. Ignore them or they will try to tell you an story of them having kidnaped somebody you know down there. Pretty common way of trying to make money nowadays down there.

That's way you heard her speaking spanish.

The 555 area code is what you call for assistance. Another words, it's like pressing the zero on your phone or dialing 411 to get a phone number.

I googled it and this is what I came up with -

Reserved for directory assistance applications

Female called @ 11pm EST saying hello in what sounded like Spanish. When I responded in English, she hung up. Where is this area code from?