Concurrent calls using VOIP provider

I’m trying to better understand how to purchase service with a VOIP provider.

If my goal is to be able to accommodate 6 to 8 simultaneous (in coming or outgoing) VOIP calls, how many accounts do I need to establish with the VOIP provider? Yesterday, a BroadVoice rep. said I would need to purchase 6 to 8 individual accounts. But, this doesn’t sound right to me.

The Asterisk system I’m planning will be for a small business near Albany, NY. Does anyone recommend a VOIP provider in this area?