Toll-free numbers are mainly used for inbound calls
Making a call from a Toll-Free number to another Toll-Free number is generally not recommended. This is because the organization responsible for the Toll-Free number, known as the RespOrg, specifies which carrier should handle the call, usually based on geographic codes like LATA or NPANXX.
Failed calls from Toll-free numbers
If only a Toll-Free number is involved, some RespOrgs might not have a set path for the call, causing it to fail with a message like "This destination is not available from your calling area." The same issue can occur with international calls to Toll-Free numbers, often because RespOrgs want to avoid the higher costs associated with routing calls from areas not covered by valid LATA or NPANXX codes.
General recommendations
Call from a valid US Automatic Number Identification (ANI). This is in line with Flowroute's Outbound ANI Requirements.
Include a valid P-Charge-Info header in the initial SIP invite; aka Billing Telephone Number (BTN), this header provides the BTN if it differs from the From number.
Utilize the P-Asserted-Identity (PAI) header in the initial SIP invite. This is a less reliable option compared to P-Charge-Info, as some carriers may remove the PAI header before routing the call.
More details
Using Toll-Free numbers as the “From” number for outgoing calls presents a unique set of challenges, primarily because the receiving end may block such calls. This is often due to the complexities of billing and routing associated with Toll-Free numbers.
To successfully complete the call, when dialing other Toll-Free numbers, it's crucial to include a valid billing telephone number in the 'p-charge-info' header of the initial SIP (Session Initiation Protocol) invite. This header serves as a mechanism for the terminating carrier to identify the billing details, therefore providing a more defined routing process.
Billing for calls made from Toll-Free numbers is particularly complicated. The rate charged to the terminating end is determined based on the 'From' number. Calls that originate from numbers without a defined location, such as other Toll-Free numbers, will likely result in a failed call. This is because Flowroute, which manages the Toll-Free number, may not have a billing identity and will not be able to create a billable receipt for the call.
To mitigate the challenges associated with missing billing rates and routing complexities, some Toll-Free numbers are configured to disallow incoming calls from numbers without a defined location. When this happens, callers may encounter an error.
When getting this error, Flowroute's system will not provide a voice error via operator recording. The call will drop the line. This is a protective measure taken by the RespOrg or the terminating carrier to avoid incurring higher costs and to simplify the routing process.
Therefore, including a valid billing telephone number in the p-charge-info header is not just a best practice but often a requirement for successful call completion. It allows the terminating carrier to accurately bill the end user and facilitates more reliable and cost-effective routing. By adhering to this practice, users can significantly improve the success rate of calls made from Toll-Free numbers, ensuring more effective and efficient communication.