An amused Mourinho says to those in attendance at the press conference: 'It's from talkSPORT.'
Then Dominic McGuinness, a talkSPORT 2 reporter, responds to Mourinho, saying: 'That shouldn't be working like that.'
And the charismatic manager then carries on in the same comical fashion. Mourinho looks at McGuinness and says: 'It's for you? Wait a second please. It's Abi from talkSPORT.'
McGuinness, who looks embarrassed by the whole situation, takes the phone and tells the caller: 'You shouldn't be doing that now, Abs. Not for now. Sorry, should have been off.'
Mourinho didn't seem too bothered by Paterson's phone call as he continues to laugh, before comically asking the media: 'What was the question?
After the humorous incident took place, Paterson took to Twitter in good spirits to post a photo of Mourinho holding up the phone with her picture on during the press conference.
She captioned the Tweet: 'At least I chose a good photo for my WhatsApp picture. What a day.'
Mourinho was speaking to the media as his United side prepare for their crunch Premier League match with rivals Liverpool.
United have been in great form recently, winning their last six league games, but they come up against a Jurgen Klopp side that sit second in the table, five points above the Old Trafford outfit.