Search terms with and without dashes.

I was led to believe that whilst constraining a search term by double quotation marks in order search for that exact term dashes are ignored.  Thus, for example, "212-M50-0599" is equivalent to “212 M50 0599”.  However what we are finding, in the case of this example, we are gettting matches to the area code 212 rather than that exact string.  Is there something that I'm missing?  I'm not sure the dashes even have anything to do with it as this is a string of ten numbers broken up in the right places.  Any guidance would be appreciated.