Jay Z reportedly has a separate phone which only Rihanna has the number for, much to his wife Beyonce's fury.
Jay Z has a phone line just for Rihanna to call.
The Roc Nation mogul has a close relationship with the 'Diamonds' hitmaker and his wife Beyonce was said to be "livid" when she discovered the singer is able to contact her husband at any time of the day.
A source said: "Jay has several phones, one of which he keeps reserved for Rihanna, supposedly to discuss business interests.
"It's obvious when she calls because he'll interrupt meetings, even walk away from the dinner table to speak with her.
"Beyonce has always been aware that he has several different numbers, but when she discovered Rihanna has a hotline to her husband, she was livid.
"She absolutely hates how close they are but feels powerless to stop it."
The two women were said to have kept their distance from one another at the launch of Jay's new streaming service, Tidal, but Beyonce - who has three-year-old daughter Blue Ivy with the '99 Problems' rapper - didn't want to cause a scene.
The source added to Grazia magazine: "Beyonce is a peacekeeper by nature. And the last thing she wants is to cause a fuss while the spotlight is on their new venture.
"But she feels increasingly frustrated that Jay refuses to accept there is anything unorthodox about his friendship with Rihanna."