Think about a phone conversation in real life. You can easily hear one side of the conversation - yours - but the other side may be more muted. You can see the things around you, but you can't see the person who is speaking, or their surroundings. If you're using a landline you're trapped, only able to move the distance of the telephone cord.
So fictional telephone conversations immediately start with problems. They're usually static situations, and halve your scope for describing what's going on. There can be no nuances of facial expression, no grimacing, no scratching of heads, no running of hands through hair (this may of course be a good thing, but I'm sure you get the idea). No clothes, no surroundings, no nothing but one person in a room talking into a phone.
If I discover I've let a phone conversation slip into the first draft I always try to manoeuvre my characters so they meet face to face. Physically being in the same space heightens the conflict, whether it's the brush off call (how are they going to get rid of this unwanted visitor?) or the arrival of a loved one (how soon can they get them in their arms?).
There are going to be times when the phone call can't be changed to a face to face meeting, or is better as a call - for example, the conflict coming from a character's longing for closeness - and if they use a mobile, then at least you can have them moving so the scene isn't static. But in general, get them turning up on each other's doorsteps whenever possible.