### Answer Yes, it's possible. Carriers can mark a number as "Spam Likely," which hurts pickup rates and can send calls to voicemail or get them rejected. How to check your number's health - Check your outbound call log for SIP error code 608. That code means the call was rejected because the number was marked as spam likely. [(1) ]() - Watch for real-time reputation alerts. Retell monitors your caller ID reputation and alerts you when numbers are at risk of being flagged. - Use external tools to gauge spam risk (results vary by carrier) : [Nomorobo]() and [IPQualityScore]() . Rule out a false "voicemail" signal Landing in voicemail isn't always a blacklist issue. On iOS 26, call screening can answer your call before a human does, and your agent may count that as answered. Add a Boolean post-call analysis category to separate real human pickups from screeners or voicemail. Example configuration: - Name: user_reached - Description: Was the user reached or not? Set to false if voicemail is detected, if you are only asked for the reason for the call, or if you are only asked to leave a message. Otherwise, set to true. Ways to improve deliverability before buying a new number - Verified Phone: Retell registers your number directly with carriers to strengthen its reputation and reduce spam flagging. - Branded Call: Recipients see your verified business name when the phone rings. - Pace your calls: Aggressive or repetitive dialing can get your calls filtered. Spread out follow-ups and use Batch Calls to schedule campaigns. - Register with freecallerregistry.com: In a community thread about a blocked Twilio number, this was suggested to restore reputation, along with checking the Twilio D

ebugger logs for error codes like 13225 (Twilio blocked) or 32017 (carrier blocked) . [(2) ]() If you've tried these and the number still has a poor reputation, I don't have documented criteria for when to replace it, so I can't say definitively that buying a new one is necessary.

​ To learn more, see the sources I considered: [[1] iOS 26 Call Screening: Best Practices for Outbound | Retell AI](https://www.retellai.com/blog/ios-call-screening) [[2] I just got sms verified on my Twilio number and today it just quit working.](https://discord.com/channels/1186424376300679209/1400221857357107250) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.