I am planning to open an account at phone.com. I have assessed how their system works and I think it is what my business needs as of the moment. Unfortunately, I am a bit confused. I have checked their website and they offer several phone units to go along their systems. Should I really use one? Can't I just use the current phone I am using? I hope someone could help me understand how VoIP really works because I think my knowledge isn't enough yet. Thanks!