One problem with phone conversations is whether you present them as one-way (one person speaking with pauses for the responses) or two-way dialogue. As long as phone conversations are integral to the story, they are a normal part of life, particularly with the level of cell phone usage. One-way conversations can be used to really ramp up suspense. This creates a consistency problem, however, if you want to present both sides of a conversation at another time. Modern phones are useful here. If you use one-way conversations, but want to slip in a two-way, just have the character push the "speaker" button on the phone.
Phone conversations are not equivalent to dreams. In the former, you are using normal dialogue in which the two speakers are not in immediate proximity. If you are writing a contemporary story, avoidance of phones may be unrealistic, particuarly if your character is under thirty years of age and unnmarried, although individuals of all ages and genders seem to be as concerned about cell phone minutes as are teenagers. These days, a cellular phone is an essential security device for many. Hands up, all those who don't have one...