I just switched my VoIP phone service from AT&T to Charter, so I'm not 100% sure. Let me check to see if it's an option on their service, etc. If not, we could do it via the internet using Skype, but doing it via "phone" might be more reliable, etc. I'll get back to you on this a.s.a.p.
I checked and Charter Telephone doesn't have the Conferencing feature for their residential service. There are however companies that provide conferencing "on the fly". I'll look into this and try to find an inexpensive option.