William Castle’s tense little 1965 thriller, “I Saw What You Did,” gets a modern makeover in this slick but overcooked horror movie about a couple of phone pranksters who get more than a taste of their own medicine. Directed by the team of Alexis Wajsbrot and Damien Mace, “Don’t Hang Up” might have worked if kept relatively simple (as Castle’s picture was), but the effort to make it bigger and grosser dooms it.

The movie stars Gregg Sulkin and Garrett Clayton as Sam and Brady, two high school jerks who, along with a few equally dumb classmates, play elaborate phone tricks that they broadcast online to attract viewers; in a prologue they impersonate police and convince a terrified woman (Sienna Guillory) that interlopers have invaded her house. Sometime later, Sam is alone at his place, brooding over being dumped by his girlfriend Peyton (Bella Dayne), when Clayton shows up. They decide to make some prank calls just as a lark, but the game backfires when a strange man on the line turns the tables, threatening them, their friends, and even Clayton’s parents. Soon they’re effectively trapped in the house as their unknown tormentor comes to seem omniscient and omnipotent, foretelling their every move and boxing them in at every turn. Bodies will shortly begin to pile up.

The picture starts out on the right foot, making Sam and Clayton so thoroughly obnoxious that you’re happy to see them suddenly become the victims rather than the perpetrators. The problem lies in the development of Joe Johnson’s script. As the story develops, the caller’s control over everything that happens grows more and more implausible, and though there is an attempt to explain that, and to provide a reason why the man is so intent on making the guys suffer, by the end the narrative has strained even the flimsiest degree of credulity past the breaking point.

That said, one has to appreciate the technical quality of the production. The directors, cinematographer Nat Hall and editors Carmela Iaudeli and Tim Morrell have fashioned a good-looking picture that moves swiftly, though not fast enough to obscure the plot holes. It’s unfortunate that the makers felt compelled to make the violence so explicit, but that seems to be obligatory nowadays; even had they wanted to depend on suspense and tension without the sudden shocks that explosions of gore provide, that approach probably wouldn’t have worked with a contemporary audience. It’s also a pity that, apart from Sulkin, the cast performs pretty much on an amateur level.

“Don’t Hang Up” is a horror thriller that shows some promise but has been tricked up to its own detriment. It seems destined to find its rightful place not in theatres but on a cable network like SyFy or Chiller.