It's unlikely the Management Company is changing. It is more likely your management Agent is changing and that is not really a big deal. It should be done every few years in my opinion. Its like moving from one electric supply to another every year, a good idea to drive value.
Anyway you should know who the management company directors are. They decide on the management fees and how money is spent. They will probably not be changing. You should be having annual AGMs and voting in these directors. You could even go forward yourself as a director and get a really good understanding of how your complex is being run