I have a 1 year old Bichon Frise and she cannot stand the sight of someone using their phone. It's not even when she was already trying to play with you and you pull out your phone, she can be laying on the coffee table while you're on the couch, she'd be doing her own thing, but the instant you start using your phone she will walk up to you, put her paws on your knees, and do that little high pitched bark thing dogs do when they want something from you. She's not okay with anyone in our family using their phones in front of her, not just me. Does this happen with anyone else's dog? Is this a symptom of insufficient enrichment and play at home or something like that where she thinks we're not paying enough attention to her and associates phone use with that?
I've never seen this behavior before, but I'd guess that she recognizes that you're giving your attention to something else and she doesn't like it. This is possibly jealousy, which can't be tolerated. You should make sure she's receiving adequate attention and stimulation, and then be firm about not allowing this behavior from her.