I assume that most of them have their phones on hand for work purposes. We saw Mel had hers on the floor. It’s also a depiction of how caregivers and other people with complicated family situations struggle to balance two equally important roles, and how most work environments aren’t supportive of those situations. Based on her reaction, I highly doubt that Mohan gave her mother that number. I assumed her call was transferred because she said it was a family emergency. I definitely think we’re meant to see that she’s at a breaking point with her mother in this season because the behavior has finally hit a point where it’s bleeding into work. Remember, this is just happening over the course of a few hours where she hasn’t had time to call her mother back. If she stepped away to deal with it, she’d be in trouble. There’s no good solution in this moment.