By default Simwood authenticates by source IP address and bills outbound calls from a given address to the appropriate account. You can differentiate between customers by giving the new IP or Auth trunk a description, as seen in the below image:
An account with a configured trunk will lose the default IP address authentication, i.e. will change from being IP address only to being IP address AND username/password.
IP address pools can be shared between multiple customers but this will require configuration by Simwood.
The various feature settings and limit settings which apply to the account as a whole can be applied to trunks as well to finely control your customer's usage of your overall Simwood capacity.
Where a trunk is used, CDRs will contain the trunk ID once the feature is enabled in the API.