Vocalocity Bills you after they terminate your service Atlanta Georgia

I was unhappy with my business VoIP phone service and cancelled by email.  I assumed when you cancel your service with a telecommunications provider they stop billing you.  Not Vocalocity - they will bill for the entire period and do not refund you.  The worst is they don't bother to tell you this when they call you to confirm your cancellation.  

They were good an disconnecting me immediately after they called to confirm my cancellation, but refused to refund me for the amount my company had paid up for the full month a the beginning of the billing cycle.   When I cancelled I thought it was effective for the next billing period, I didn't realize you had to specifically state that. They kep using the word immediately, but didn't explain what that meant.  

When i called customer serivce they had no idea what to say and switched me over to billing  They guy in billing just kept repeating himself that they cancelled my service immediately, but they still billed me when I had no service.  Isn't this illegal to bill for phone service when the phones have been turned off? This seems to be a very shady business practice.