Toll Free: These are numbers where the user is not dialed but you as a client gets billed for incoming calls.
Premium: these are numbers where the client is billed above normal rates and Client's account billed for incoming calls
Regular: The user is billed normal call rates and the Client's account billed for incoming and outgoing calls
SIP Uses the internet Client’s account is billed for incoming and outgoing calls
Virtualized Physical Lines Billed normal call rates Client's account billed for incoming and outgoing calls
You can find the charges for the voice numbers here.
N.B - Toll-Free(0800), Premium Numbers(0900) and virtualized numbers do not make outgoing calls but the regular numbers attached to them(also known as hunting numbers) can make the outgoing calls. This is how the calls will be charged to the client's account.
Need more info ? email voice@africastalking.com