### Answer I don't have specific information about "Signal House Number" in the available sources. However, Retell AI supports connecting custom telephony providers through two main methods [(1) ]() : *Method 1: Elastic SIP Trunking (Recommended) * You can connect any telephony provider that supports elastic SIP trunking by: - Setting up a SIP trunk with your provider - Configuring your number to point to Retell's SIP server:

sip.retellai.com

- Importing that number into Retell Method 2: Dial to SIP URI If elastic SIP trunking isn't supported, you can dial calls directly to Retell's SIP URI Retell SIP Details: - SIP server URI:

sip.retellai.com

- IP ranges:

18.98.16.120/30

(all regions) ,

143.223.88.0/21

(certain US traffic) ,

161.115.160.0/19

(certain US traffic) - Supported transports: TCP (recommended) , UDP, TLS, mTLS - Supported codecs: PCMU, PCMA, G.722 If Signal House supports SIP trunking or can dial to a SIP URI, you should be able to connect it to Retell AI using one of these methods. I'd recommend checking with Signal House to confirm their SIP capabilities.

​ To learn more, see the sources I considered: [[1] Custom Telephony Overview](https://docs.retellai.com/deploy/custom-telephony) ​

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

### Answer Each workspace in Retell AI requires its own separate payment method [(1) ]() . Payment methods are not shared between workspaces [(2) ]() . When you create a new workspace for your client, that workspace operates independently with its own billing configuration [(1) ]() . The payment methods attached to your original workspace don't automatically carry over to the new one [(2) ]() . To purchase a phone number in the new workspace, you need to add a payment method specifically to that workspace before buying numbers [(3) ]() . This is required because each workspace maintains separate billing [(1) ]() . To resolve this: 1. Navigate to the new workspace's "Billing" tab 2. Add a payment method for that specific workspace 3. Once added, you'll be able to purchase phone numbers [(3) ]() This workspace separation is intentional - it allows agencies and companies to manage billing independently for different clients or locations [(2) ]() .

​ To learn more, see the sources I considered: [[1] Create and manage Retell workspaces](https://docs.retellai.com/accounts/workspace) [[2] Billing Question](https://discord.com/channels/1186424376300679209/1388977364880588960) [[3] AI Phone Numbers: How to Buy & Set Up | Retell AI](https://www.retellai.com/blog/how-to-buy-an-ai-phone-number-a-guide-on-your-options-and-providers) ​

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

### Answer Based on similar issues reported by other users, here are some troubleshooting steps: Try removing and re-adding the payment method: [(1) ]() 1. Go to the Billing tab in your workspace dashboard [(2) ]() 2. Click "Change payment methods" to access Stripe 3. Try to remove the payment method and add it again [(1) ]() Note: If you see an error saying "Your default payment method can't be deleted because you have an active plan," this indicates the payment method is registered but there may be a synchronization issue . Additional steps to try: - Refresh your browser or clear cache - Log out and log back into the workspace - Verify the payment method shows as "default" in the Stripe portal - Ensure you're in the correct workspace (not your original one) If the issue persists after trying these steps, this appears to be a billing system synchronization problem that requires support assistance [(3) ]() . You can reach out to Retell AI support for help resolving account access and billing issues . The payment method must be successfully added before you can purchase phone numbers, as adding a payment method is required to continue using Retell services and purchase phone numbers [(2) ]() [(4) ]() .

​ To learn more, see the sources I considered: [[1] Problem with billing](https://discord.com/channels/1186424376300679209/1341565628238135368) [[2] Add payment methods](https://docs.retellai.com/accounts/add-payment) [[3] About the Billing and Account Related category](https://community.retellai.com/t/about-the-billing-and-account-related-category/35) [[4] AI Phone Numbers: How to Buy & Set Up | Retell AI](https://www.retellai.com/blog/how-to-buy-an-ai-phone-number-a-guide-on-your-options-and-providers) ​

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