A woman getting her phone repaired in a Harlem store was murdered by a man who walked in, stabbed her three times and calmly walked right out again just after noon Saturday.

Police later arrested Pedro Vinent-Barcia, 62, and they are looking into reports that he and the 51-year-old victim, whose name was withheld pending family notification, were an item, a source said.

Sam Saleh, whose family owns the store at 2253 Third Ave., quoted an employee as saying, “the guy walked in and stabbed her and walked out like he didn’t do anything.’’