Last month the “Twilight” couple split up after Stewart admitted to having an affair with “Snow-white and the Huntsman” director Rupert Sanders.
Since news of the affair broke, Pattinson is supposed to have changed his number four times, in his attempts to avoid his ex-girlfriend.
"Rob's actually launched an investigation of his close friends, business associates - even his family - to find out who is leaking his numbers to Kristen," an insider told National Enquirer. "It's only 20 close confidants and one of them is betraying him."
The magazine claims the actor is willing to take drastic steps to ensure his ex-girlfriend can no longer contact him.
"He's steaming mad and swears that when he finds the culprit, he'll cut that person out of his life," the source said.
Stewart made her first public appearance since the scandal broke last week, promoting her latest movie “On the Road” at the Toronto Film Festival.