That kind of recurring dream usually connects to a feeling of helplessness about something you consider important in your daily life. It's not really about the phone itself, but what it represents: your ability to respond, to be available, to do what's expected of you. And of course, when the dream happens right after stressful work situations like that video call with the client, it's because your head is processing that vulnerability very literally.
What's interesting is that these dreams tend to intensify when we have several things hanging over us at once and we feel dependent on something (a tool, communication, a resource) that we perceive as fragile or potentially out of reach. In your specific case, the pattern you mentioned - that it happens right at important moments - suggests there's probably some anxiety about losing opportunities or disappointing someone at work. It doesn't necessarily mean it'll happen, but your subconscious is rehearsing the worst-case scenario.
What could help you is asking yourself what's actually going on at work or in your life right now. Is there something pending that has you on edge? Do you feel pressure to maintain a certain image or level of performance? Sometimes these dreams disappear on their own once we resolve the situation that's causing them, or at least once we stop living it so intensely.