The emphasis in the film on the use of video chat to explore the narrative is novel. I hope you enjoy novelty, because for much of the length that's the chief draw that 'Chatter' has going for it. Yet while the pace is sluggish, and the content a bit of a slog, there's just enough gradual paranormal progression to keep us invested.
It's a decent concept, though the execution tends to struggle to particularly grab us. What little we see that takes place in a space outside the monitored conversations is largely schlocky or wholly superfluous, serving little purpose except exposition or a rudimentary framework for the feature. Exchanges seen in the video chat format are at first very mundane and awkward, and I'm not sure which is worse - that these moments may have been hammed up for the film, or that they may be a reflection of the sort of conversations people actually have. I really don't know which is true.
For much of the length, 'Chatter' is merely a slow, low-key meandering of interpersonal drama. There are abnormal goings-on that steadily grow more creepy and dire as the scattershot story progresses, though the connecting threads between incidents is sometimes tenuous and less than convincing. Still, in the last 20-30 minutes, supernatural eventfulness ramps up, resulting in modest tension and spooky fun if you can get through the early scenes.
The cameras focus concretely on stars Brady Smith and Sarena Khan. I can't say I'm familiar with either, but both do a fine job of realizing the awkward long-distance relationship of David and Laura, and the mounting distress. They ably demonstrate a measure of range and nuance to navigate changing, conflicting emotions, and though the finale forces them into typical Horror Protagonist parts, they do well by it.
The film's approach to its narrative, giving us simple peeks into home or office settings, means that apart from adequate special effects, nothing especially stands out in terms of the technical craft. And I suppose that's rather the story of this movie as a whole: take away the video chat element that defines it, and there's nothing at all remarkable about the feature. Even as it labors through early lethargy, it's not bad, but unless one is a particular fan of someone in the cast or crew, nor is there any specific reason to watch this over any other title playing in a similar space. All that said - don't go out of your way by any means, but 'Chatter' is sufficiently engaging to at least keep us watching, and ultimately suitable genre entertainment that's an okay watch of you come across it.