That depends. Using your Internet connection as your telephone circuit has it's pluses and minuses. The typical business has on average an internet connection of, for purposes of this discussion, 1 mb/s. (Most have 768 kb/s or 1.544 mbs/). If the average VoIP call requires 64kb/s, then a 1mb/s Internet connection can support 16 simultaneous calls and nothing else. If half your 1mb/s connection was used for web surfing, email and download, and the other half for phone calls, then your connection can only support 8 phone calls.