Should I Be Worried?

I Keep Getting These Phone Calls From Someone Called Olivia, She Told Me That I Have Had With Her Brother Called Dom, She Knows My Name My Nickname And Most Of My Mates Names? Strange Yeah ?? Im Getting REally Worried But Everyone Is Telling Me Not to Get So Wound Up As It Is Only Some Pathetic Person Messing About? How Did She Get My Number And How Does She Know So Much About Me? I Try To Ring Her Up But She Hangs Up On Me Should I Be Worried ?