• Billing Telephone Number (BTN): This is the primary telephone number associated with an account that is used for billing purposes. The BTN is the main identifier for the account and is used by the service provider to organize and manage billing information. When multiple lines or services are associated with a single account, the BTN serves as the key reference number for billing inquiries, payments, and account management.

• Account Telephone Number (ATN): This refers to any additional telephone numbers that are linked to the same account but are not the primary billing number. An account might have multiple ATNs if there are several lines or services (like fax lines, secondary phone lines, etc.) under the same account. These ATNs are billed together under the primary BTN.

In a typical scenario, a customer or business might have several telephone lines or services, each with its own telephone number (the ATNs), but for convenience and simplicity, they are all billed under a single main number, the BTN. This arrangement simplifies billing and account management for both the customer and the service provider.