A callback URL can be configured for an existing SMS service plan. This is the URL to which delivery receipts and incoming messages will be sent. You can also update an existing callback URL for an existing service plan.
To configure the callback URL for a service plan:
- Log in to the Sinch Build Dashboard.
- Select SMS from the left menu and select the Service APIs option. The Service APIs page is displayed:

Click the service (either the NAME or the SERVICE PLAN ID) to which the callback URL is to be assigned.
- The REST API details page is displayed:

- Navigate to the Callback URLs section and click Add callback URL.

- The Default URL, Outgoing URL, and Incoming URL fields are displayed:

- To direct incoming messages and delivery reports to a single URL, populate the Default URL field. Note that this setting will be overridden by the values provided in the Outgoing URL field and/or the Incoming URL field.
- To direct delivery reports and message delivery confirmations to a specific URL, populate the Outgoing URL field. Note that this will override the value provided in the Default URL field for delivery reports and message delivery confirmations.
- To direct incoming messages and responses to a specific URL, populate the Incoming URL field. Note that this will override the value provided in the Default URL field for incoming messages and responses.
Once you have populated the appropriate fields, click Configure.
In addition to setting the callback URL for an existing SMS service plan, you can also assign a virtual number to an SMS service plan.