Your SIP trunk service is set up based on the route plans from your original order. Using Control Center, you can add a phone number to your SIP trunk service.
To add a phone numbers to your SIP trunk service:
Control Center displays a list of all services assigned to the accounts under your enterprise ID. If you have more than 10 services, you can view the rest of your services by clicking one of the blue linked Show numbers at the top of the list or you can click the blue down arrow at the bottom of the list to add 10 services at a time to the view.