Stakeout (1987) on Netflix

After a brutal murderer escaped from prison, it is ordered that all of his possible contacts are put under survey. His former girlfriend Maria McGuire, who ceased contact with him long ago, is observed by four cops. The night-team is formed by Chris Leece and Bill Reimers, who work as partners normally, too. Maria proves to be a very cute young woman, and Chris, who bugs her appartment as Telephone-Bill, falls for her. Now, everytime he is with her, his partner has to watch his friend enjoy life and he himself has to get out before the other team comes in. But when Maria's ex arrives surprisingly, Telephone Bill and his partner find themselves in deep trouble.