The reseller and customer features are complicated.
As a master account, you can create a reseller or a customer account.
Reseller accounts can create customer accounts. Masters can also create customer accounts
Billing is separate for each account type. So if a master creates a reseller and the reseller creates a customer, you have 3 layers of billing: Master -> Reseller -> Customer
Or if a Master creates a Customer: Master -> Customer
When a call is placed, a CDR record is created for all three accounts.
So remember, when creating a Customer or a Reseller, think about what you're trying to accomplish.