----------------------------- **While I generate an answer, here are some sources that might be helpful**: * [Call Forwarding]() * [Function Calling]() * [Create Phone Call]() * [Phone Calling]() -----------------------------

### Answer To address your concerns regarding call forwarding with Vapi: 1. **Call Forwarding Process**: Vapi allows you to set up call forwarding using the attributes

forwardingPhoneNumbers

for multiple numbers or

forwardingPhoneNumber

for a single number. These settings can be configured via the API, and you do not necessarily require access from the dashboard to set this up [(1)]() . 2. **Custom Backend Requirement**: Using a custom backend is not mandatory for call forwarding. However, for more complex scenarios or dynamic number handling, integrating a custom server might be beneficial. This server can interact with Vapi using the

serverUrl

you specify, which allows more dynamic responses and functionalities . 3. **Issue with Calls Hanging Up**: If the call forwarding function is triggered but results in the call hanging up, it might be due to the configuration of the forwarding settings or issues with the provider settings. Make sure that the phone numbers are correctly formatted (E.164 format) and that the backend handling the forwarding (if any) is correctly processing the calls . 4. **Requirement for Twilio Numbers**: Forwarded numbers do not necessarily need to be Twilio numbers. Vapi can forward calls to any valid phone number. The key is to ensure that the number is supported by your current telephony infrastructure and is correctly set up for international or local forwarding as needed . 5. **Handling Dynamic Numbers**: For dynamic number forwarding, you can programatically update the

forwardingPhoneNumber

or

forwardingPhoneNumbers

attributes based on the logic defined in your backend. This can be effectively managed by setting conditions in the system to select the appropriate number based on the interaction context or other criteria . If you continue to experience issues, ensure that your setup ali

gns with the configuration guidelines provided in the documentation and that all numbers are correctly formatted and supported by your telephony provider.

Got it. Tagging @User for additional help.