The first thing that must be done to fix this problem is to properly understand it. Within the context of teams and teamwork, there are many different types of communication problems that can arise. There is no way to fix the problem if you do not understand its exact nature. Therefore, the first thing to do when trying to fix the problem is to observe the team and to determine what sort of problem it is experiencing.
Once the problem is diagnosed, the solution will obviously be different depending on the nature of the problem. For example, it is possible that the problem is due to a lack of rules (or a lack of understanding of those rules). There might be a problem because some members of the team are communicating (by email, for example) only with certain other members and not with the whole team. This can be rectified by setting up and enforcing rules that make it clear that all communications must be directed to all members of the team.
Another possible problem would be that team members need more training in communication skills. For example, at meetings, team members might be doing too much talking and not enough listening to one another. In such a case, it seems likely that some degree of training will be needed in order to get members to see how their habits are unproductive and to help them change those habits.
Thus, the only thing that we can say for sure is that we need to assess the situation and determine what the problem is. Once the problem is identified, there can be many possible ways to fix it.