I copied google's "I'll call a cop" which was marked wrong, but might be a better translation. Is "poliziotto" used is Italian as "cop" is used in English or are there different informal terms for the police in Italian?
I'm not sure about how "cop" is used, is it pejorative?
Anyway other Italian word to express the police officer are:
"agente di polizia", very formal;
"poliziotto" = most common, not very formal, but absolutely not pejorative: it's usally used writing news stories.
"gendarme" = antiquated, meaning something like "man of army";
"piedipiatti" = humorously used or pejorative;
"questurino"/"celerino" = popular, colloquial, sometimes used in newspapers.
"sbirro" = very pejorative.
Canadian native. "Cop" is informal and can be pejorative with intonation. I used "I will call the police" and it was not accepted because it is a "pluralized noun". I would not normally say "I will call A policeman". Here (rural Canada) they come in cars and are dispatched by a central call number. In the bigger centers there are officers on foot. I am pretty sure whichever form was used, intent would be established. ;) Other pejoratives are "pigs", "hogs", "smokies".