Resolve spam labels and blocked calls

Carrier analytics can affect your outbound calls in two ways. A labeled call still rings, but the recipient’s phone shows a warning such as Spam, Scam Likely, or Spam Risk. A blocked call never rings, because the destination network rejects it and your application sees a failed call. The two problems share most of their causes and fixes, so this guide covers both. It shows how to tell them apart, how to read the SIP response that points to the blocking provider, and how to request STIR/SHAKEN “A” attestation, update your CNAM, and submit corrections to the providers that label and block calls.

Labeled or blocked

Work out which problem you have before you change anything. A blocked call usually shows up as “we can’t call this number” rather than “we’re flagged as spam”, and its fix starts in a different place.

Diagnose a blocked call from its SIP response

A blocked call fails with a SIP response code, and some of those responses carry the blocking provider’s dispute contact. FCC rules require a terminating provider that blocks calls based on an analytics program to return a response code to the origination point of the call. On IP networks, that code is SIP 603+ as defined in ATIS-1000099 (47 CFR 64.1200(k)(9)).

To get the response for a failed call, open Logs in your SignalWire Dashboard, select the call, and copy its Segment ID. Then open a ticket with SignalWire Support. Include two or three Segment IDs, or exact timestamps with a time zone, and ask for the SIP response code and Reason header that the destination network returned.

603 with an analytics Reason header

A 603+ response carries a Reason header whose text value starts with v=analytics1. It includes a redress contact, usually a url, and can include an id that identifies the block when you file a dispute. The contact arrives inside the rejection itself, so you don’t have to guess which provider blocked the call.

Reason: SIP;cause=603;text="v=analytics1;url=https://example.com/redress;id=ABC123"

607 Unwanted

RFC 8197 defines 607 Unwanted as the way a called party indicates that a call was unwanted. The recipient’s phone or app sends it, based on the user’s input or its own logic. A service provider can weigh 607 responses when it decides how to handle future calls from the same caller, so a pattern of them points to a consent or calling-pattern problem.

608 Rejected

RFC 8688 defines 608 Rejected for calls that an intermediary rejects on the called user’s behalf, with an analytics engine as the first use case. The intermediary adds a Call-Info header with purpose=jwscard. It points to a signed jCard with the intermediary’s contact details, such as a URL, email address, or phone number, so you can reach the entity that blocked the call in error. In the US, FCC rules now require a terminating provider that blocks calls based on analytics to return 603+ instead.

Identify who applied a label

The exact wording of a label can tell you which system applied it, so ask the recipient for a screenshot. Verizon lists its spam labels as Potential Spam, Potential Fraud, Robo caller, and SPAM?. A call with a different label, such as SPAM LIKELY, was not labeled by Verizon, and Verizon directs recipients to check with their spam protection service provider instead.

Most reports name the carrier (“Verizon flags our calls”) rather than the analytics provider. Use this table to find who to contact.

Remediation steps

Hello,
We are the current authorized user of the phone number(s) listed below. These numbers are
assigned to [Business Name] and are used for [call purpose, such as customer support callbacks,
appointment confirmations, billing follow-up, or account notifications].
The numbers appear to be incorrectly labeled as spam, scam, or fraud. We believe this labeling
is inaccurate and may have been inherited from prior use before the numbers were assigned to us.
Please review and remove any inaccurate spam, scam, or fraud labeling associated with these numbers.
Business name: [Business Name]
Website: [Website]
Phone numbers: [List of Numbers]
Call purpose: [Call Purpose]
Carrier/provider: SignalWire
Contact name: [Name]
Contact email: [Email]
Contact phone: [Phone]
Thank you.

Your rights when a carrier blocks calls in error

FCC rules give callers a dispute route with the terminating provider that blocked the call (47 CFR 64.1200(k)(8)). A terminating provider that blocks calls under that section must publish a single point of contact on its website for call blocking error complaints. When it determines that a credible claim of erroneous blocking is correct, it must promptly stop the call treatment for that number unless circumstances change. It may not charge you for reporting, investigating, or resolving a complaint made in good faith.

Confirm the result

A dispute or registration is only finished when the calls behave differently, so test each affected path.

For blocked calls, place a new test call to a destination that failed before. If it fails again, collect its Segment ID and ask SignalWire Support for the new SIP response. A 603+ that still carries a Reason header means the block is still in place, and its redress contact tells you who to follow up with.

For labels, the recipient’s phone is the place to check. Call a handset on each affected carrier’s network and look at what it displays. First Orion’s free watchlist reports when registered numbers are tagged as potential spam on T-Mobile, and the paid services listed later on this page include caller reputation monitoring.

Why a resolved label or block can return

A successful dispute removes the current treatment. It doesn’t change the calling behavior that triggered it. The FCC rule has a provider stop the call treatment for a number “unless circumstances change”, and Verizon warns that a feedback submission may not change how future calls are labeled. If your numbers keep calling the way they did before, expect the label or block to come back. The practices in the next section are what keep a corrected number in good standing.

Outbound Calling Best Practices

Even after CNAM and reputation corrections are submitted, calling behavior can flag numbers again.

Avoid these patterns:

• High-volume calling from newly assigned numbers
• Repeated redial attempts in a short time
• Very short calls and abandoned calls
• Calling people who are not expecting contact
• Inconsistent caller ID usage
• Rotating through large pools of numbers to reach the same recipients
• Calling outside reasonable local hours
• Failing to identify your business at the start of the call

Instead, follow these practices:

• Call only people who expect or have consented to the call
• Clearly identify your business at the beginning of the call
• Use consistent caller ID numbers
• Keep CNAM aligned with your actual business identity
• Monitor answer rates and complaint patterns
• Ramp traffic gradually on newly assigned numbers

What SignalWire can and can’t do

SignalWire can review your account for STIR/SHAKEN A attestation, set CNAM where your number’s carrier supports it, and confirm that your numbers are assigned to you. SignalWire Support can also investigate a failed call from its Segment ID, which is how you get the SIP response described in Diagnose a blocked call from its SIP response.

SignalWire can’t remove a label or a block that another carrier or reputation provider applied.

Optional paid reputation and branded calling services

Several reputation providers offer commercial products for businesses that rely heavily on outbound calling.

Next steps