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

### Answer I don't have any information about Mango Office integration with Retell AI in the available sources. The documentation mentions supported telephony providers like Twilio, Telnyx, and Vonage [(1) ]() [(2) ]() , but there is no mention of Mango Office specifically. Given what Mango Office support told you about their services operating only within the Russian Federation and potential incompatibility with foreign services, this appears to be a regional restriction on their end rather than a Retell AI limitation. I cannot provide a "100% guarantee" about Mango Office integration because: 1. The available sources don't document Mango Office as a supported provider 2. The restriction you described comes from Mango Office's side If you need Russian telephony support, you may want to explore whether any of the documented providers (Twilio, Telnyx, Vonage) offer coverage in your region, or contact Retell AI support directly to discuss custom telephony options. Check out these potentially useful sources: - [How to Choose the Right Telephony System in 2024]() - [Voice API: Integrate Phone AI Agents with Your System]() - [Connect AI call agent to Telnyx]() Would you like me to provide a general answer about custom telephony integration options with Retell AI?

​ To learn more, see the sources I considered: [[1] How to Choose the Right Telephony System in 2024 | Retell AI](https://www.retellai.com/blog/how-to-choose-the-right-telephony-system-in-2024) [[2] Voice API: Integrate Phone AI Agents with Your System | Retell AI](https://www.retellai.com/blog/how-to-integrate-phone-ai-agents-with-your-existing-api-systems) ​

@AI Evy Twilio, Telnyx, Vonage - thats all?

### Answer No, those aren't the only options. Retell AI supports any telephony provider that offers elastic SIP trunking. [(1) ]() [(2) ]() Twilio, Telnyx, and Vonage are simply the providers with detailed setup guides in the documentation. [(1) ]() If your telephony provider supports elastic SIP trunking, you can connect it to Retell AI by: 1. Setting up a SIP trunk with your provider 2. Configuring termination (outbound) and origination (inbound) URIs 3. Importing your phone numbers into Retell AI [(1) ]() [(3) ]() If you're having trouble with a provider that requires static IP addresses, Retell AI partners with [Jambonz]() , which supports static IP and mutual TLS, and already connects with Retell. [(1) ]() Alternatively, if your provider doesn't support elastic SIP trunking, you can use the "Dial to SIP URI" method, which requires some custom code to handle the integration.

​ To learn more, see the sources I considered: [[1] Custom Telephony Overview](https://docs.retellai.com/deploy/custom-telephony) [[2] Does Retell AI accept SIP connections from custom Telephony Providers apart from Telnyx and Twilio?](https://discord.com/channels/1186424376300679209/1393228893569421352) [[3] AI in SIP Calling & Telephony Solutions | Retell AI](https://www.retellai.com/blog/integrating-ai-with-sip-trunking-and-modern-telephony) ​

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