Vonage (bring your own number)

The Vonage connection uses a SIP trunk to route a number you already control to a ThunderPhone agent. Vonage remains the telephony provider for the number and trunk, while ThunderPhone controls the agent prompt, voice behavior, attached knowledge, and call handling. Once the imported number passes verification, it can be used for inbound and outbound calls.

What the Vonage connection does on ThunderPhone

Vonage connects over SIP. In ThunderPhone's VoIP setup, Vonage has its own tile that opens the manual SIP form with Vonage-specific steps, and the saved connection is a manual SIP configuration. This distinction matters: the integration is trunk-level call connectivity, not an API-key account connection or a native synchronization of your Vonage account or its business data.

The connection records the SIP domain or URI, optional username and password, port, transport, and an optional allowed-source-IP list. ThunderPhone can generate provider-specific setup instructions for the configuration required on the trunk side. Before saving, Test & Save Connection checks that the SIP domain resolves to a public address and, for TCP or TLS, accepts a connection on the chosen port (UDP gets the DNS check only). It cannot place a call yet, because the connection has no numbers.

Once connected, import the number. Importing verifies it: ThunderPhone places a short test call from the number, through your Vonage trunk, to a ThunderPhone number. That proves the outbound path, including your credentials, trunk selection and whether the carrier accepts the call; the number becomes active only after it passes. It does not call your number, so it does not test inbound routing. To prove that, call the number from any phone and confirm the assigned inbound agent answers. You can then assign separate inbound and outbound agents if the two directions need different prompts.

Typical call flows

After-hours call handling

A caller dials the same Vonage number the business already uses. The trunk sends the call to the assigned ThunderPhone inbound agent, which follows its deployed instructions to answer routine questions, collect caller details, or route urgent requests. This supports after-hours answering without asking callers to learn a new number.

Screening and routing

The agent can ask why the caller is contacting the business, capture the relevant context, and follow prompt-defined routing rules. If the call should reach a person, the agent can transfer it according to the configured behavior. An attended warm transfer requires an eligible production number that can place an outbound SIP leg, so confirm that capability during testing. See call screening and routing for the broader workflow.

Outbound reminders

A verified imported number can also be assigned to an outbound agent. ThunderPhone places the call through the connected trunk, the agent follows its outbound prompt, and voicemail behavior follows the agent's configuration. A separate webhook endpoint can receive call events for downstream processing; the SIP connection itself does not update an external application.

Setup outline

In your Vonage environment, identify the SIP trunk and the number you intend to route. Confirm that the trunk is authorized for the inbound and outbound directions you need.
In ThunderPhone, open Connections → VoIP, choose New connection, then Connect a provider you already use, then Vonage.
In the Vonage SIP Trunking dashboard, create a trunk and add outbound credentials. Enter the trunk's domain (for example your-trunk.sip-us.vonage.com, or the sip-eu or sip-ap region) and those credentials, plus port and transport if needed. Add allowed source IPs where your network policy uses an allowlist.
On the trunk, add the ThunderPhone SIP endpoint shown on the form as the inbound SIP URI, and link your Vonage numbers to the trunk. The form links Vonage's guide, and Generate AI Setup Guide can write step-by-step instructions.
Select Test & Save Connection. If it fails, correct the SIP domain, port or transport, or the network path to it, and test again.
Import the number from Phone Numbers → Add number → Import existing numbers. Its verification call tests the outbound path; if it fails, correct the outbound credentials or trunk settings and verify again. Then assign the appropriate agents.
Call the number from any phone to confirm inbound routing; if it does not reach ThunderPhone, check the number-to-trunk link, the inbound SIP URI and any source restriction. Then test inbound pickup, outbound caller authorization, voicemail handling, and any transfers before launch.

Check the current ThunderPhone VoIP screen for the latest steps before setup. Telephony and number charges depend on your Vonage configuration.