Call blocking and whitelisting links


David Preo


What are carriers doing to block calls if they appear unwanted or fraudulent?

In an effort to protect consumers against abusive robocalls, carriers are increasingly implementing call blocking programs.

In recent weeks, Bandwidth has observed AT&T, Verizon and T-Mobile increasingly blocking calls that they feel fit typical robocalling campaign characteristics, such as high-volume, short-duration calls originating from a single number. When implemented, a common effect of these call blocks will be a very high volume of SIP 486 (Busy Here) response codes being delivered.

What if I have legitimate outbound calling use cases?

There are many, many legitimate use cases for high-volume, short-duration calls, including school closing notifications, weather alerts, and patient reminders. These are entirely valid and legitimate use cases where recipients want to receive these calls and have opted-in to do so. However, when viewed en-masse at the network level, they can look like illegal robocalling.

In order to ensure your outbound calls aren't miscategorized as unwanted or fraudulent calls by the wireless carriers, we highly encourage you to proactively request whitelisting of legitimate outbound calling use cases from each of the major wireless carriers.

Here are the websites where you can submit whitelisting requests:

What is Bandwidth doing to fight robocalling? 

Bandwidth is working hard to prevent fraud and abuse, while simultaneously enabling a fair competitive landscape for the delivery of valid traffic. Bandwidth is actively engaged with the Federal Communications Commission (FCC), as well as with several STIR/SHAKEN working groups, to help shape and establish an industry solution for validating phone numbers and caller authenticity in an effort to reduce instances of robocalls and spoofing. We're working alongside other major service providers to develop and implement solutions that'll best suit our customers’ needs and their wide variety of use cases.

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