Guardiola had already banned Sky Sports from one media conference this season and snapped back at a reporter from the media organisation on Wednesday.
Asked about City's interest in Bournemouth attacker Antoine Semenyo, Guardiola replied: "You are from Sky, right? OK, good.
"I have to be careful what I say. After that, it is completely the opposite (of) what you write and put on the screen.
"That is why I said yesterday before and the day of the game - the transfer window is completely closed right now."
Asked about the title race, Guardiola also said: "A few weeks ago it was just Arsenal, two days ago it was three (with City and Aston Villa) and now two so we will see.
"Sunderland are so tough. I remember in my first season when I went there the crowd was unbelievable. They have beaten Newcastle, plus Arsenal and Aston Villa could not win there. It will be really difficult but at the same time we are ready."