Fuck with
Definition 1 of 3
Pro Tip 1/3Negative Connotation
This phrase usually implies someone is causing trouble or annoyance. 
Quit fucking with the TV signal, I'm trying to watch the game.
Pro Tip 2/3Aggression Warning
It can be a warning not to provoke someone or something. 
Don't fuck with the dog; he bites when he's scared.
Pro Tip 3/3Frustration Expression
Often expresses the speaker's frustration with someone's actions. 
I'm really tired of them fucking with my schedule every week!