Routing Inbound Calls Based on DID Numbers

Posted on May 19, 2023

Today, businesses with multiple inbound phones often implement an automated response or extension system to ensure calls can reach their recipient. This works well, but when callers reach a complex interactive voice response or auto-attendant system, it can make them more likely to hang up and call another business—one that might offer a faster response from a live representative. 

A study from Gartner found that consumers are less likely to do business with a company that requires a high-effort calling process rather than a low-effort experience. You can reduce customer effort for your client or company and streamline the inbound calling process by implementing a direct inward dialing (DID) solution.

A DID solution is easy to implement with a phone number API. It provides a seamless calling experience, allowing callers to dial the recipient’s number without an extension and without selecting options from an IVR or receptionist. It can improve your client or business’s customer service capabilities. We will explore DID, how it works, its benefits, and how you can integrate a DID solution using a phone number API.

What Is DID and How Does it Work?

Direct inward dialing allows inbound calls to be routed directly to a phone number without requiring an extension, receptionist, or auto-attendant solution. In the past, businesses could only integrate DID with a private branch exchange (PBX) or by using trunks from the traditional phone carrier on a primary rate interface (PRI). These options could be costly, time-consuming to integrate, and difficult to scale. 

However, cloud-based communication platforms offer the service virtually using session initiation protocol (SIP) trunking and Voice over Internet Protocol (VoIP). With SIP trunking, DID can also offer internet fax service, allowing inbound faxes to reach the correct recipient rather than a central location.

Integrating and setting up your DID is simple when you purchase a cloud-based SIP from a reputable provider. Procure new numbers or port over existing numbers from your management portal. You can often select whether the DID will have texting capabilities or only VoIP, and choose from local, international, and toll-free numbers. If you are managing high volumes of phone numbers for a business or client, you can also use a phone number API to streamline DID number assignment.

Why Are Companies Choosing DID Over Alternative Inbound Calling Methods?

Companies prefer DID to make dialing within the business and the inbound calling experience more streamlined and simple. There is no need for costly IVRs, auto-attendant systems, or extensions to receive calls and route callers to the correct recipient. 

Related: What Is a Phone Call API?

Customers value response speed and would rather work with a company that lets them speak with a representative faster. According to a report in Forbes, half of the consumers surveyed said that they would not do business with a company that takes longer to respond than expected. Calling the recipient directly using a DID offers a streamlined, more positive customer experience compared to alternatives.

What Are the Benefits of DID?

While DID is often more responsive and customer-friendly than alternatives, it also offers other inherent advantages. Integrating DID into your business or client’s communications can be simple and, when you choose a reputable provider for your SIP and phone numbers, offers the following:


When using DID with a reliable network, you’ll be guaranteed inbound calls are received. Reliable networks have redundancy built in with physical failover connections when there is a failure or interruption. Some of the best services offer 24/7 uptime and 99.999% reliability.


DID eliminates the need for costly live receptionists, answering systems, and auto attendants. Calls are automatically routed to the correct recipient without the need for intervention. Since the service is provided in the cloud when you partner with a metered or per-minute telecommunications platform, you can scale without any hidden fees and pay only for the time your client or business uses.


DID can support several types of configurations. It offers the flexibility needed for businesses to use texting, video calling, conference calling, and international and toll-free numbers. With a phone number API, you can seamlessly integrate company phone numbers into the DID system, including any vanity numbers, call masking features, international, 10-digit long code (10DLC), and toll-free numbers. It can also work alongside other APIs like SMS/MMS and SIP.


Numbers from other carriers can be quickly ported into DID when you choose a leading platform. Your business’s DID can work with its existing carrier and PBX or replace your current systems if desired.

Improved Customer Service

Callers enjoy the fast and effortless experience of calling a business with a DID solution. There is no need for complex auto-attendant or IVR systems that confuse and irritate callers. Your client or business will not need to hire a costly live representative. 

Related: Enterprise SIP Trunking: A Guide to Phone Numbers

Calling a DID offers a more personalized experience for customers and allows them to follow up easily. DID can also be customized based on preferred branch or language, so callers do not need to choose their preferences from an operator or IVR.

Disaster Recovery

Your business or client implements inherent business continuity when you add DID to a phone system. A DID means that users don’t need to be in the office to receive inbound calls, ensuring that business operations can continue remotely or at another worksite during a pandemic, fire, natural disaster, or another major event. Calls will be routed to the necessary phone without requiring days of waiting for an inbound number to be ported to another carrier network.

Unified Communications

Since DID works with internet fax, SMS/MMS, and voice service, your client or business will have seamless control of their communications. It makes calling and collaborating with users within the company simple. Each contact is included in the IP phone or VoIP telephony app.

Integrating DID Calling With a Phone Number API

If you are a developer implementing a DID phone system for a client or company, you can provide various advantages and integrate the system easily with a phone number API. The following considerations will help you do this.

Choose a Platform that Offers a REST API

A phone number API written in representational state transfer (REST) architecture will make it easier to implement in your preferred programming language. REST APIs offer exceptional compatibility, using standard HTTP commands like get and put, and popular data types like HTML and XML that make it compatible with a range of languages and applications. They are also resource friendly as they use little bandwidth and do not store states on the server side. A REST API is often the best choice for communications.

Look Over the Documentation

An API provider that offers adequate documentation can make implementing, configuring, and testing the API for your business or clients needs easier. An excellent API provider will offer helpful documentation like articles, guides, and quickstarts that make it easy to drop in microservices to perform actions like mask phone numbers or implement e911. Make sure your provider offers guides in the language of your choice, such as .NET, Ruby, and Python. Since the API is maintained by a provider, a version-controlled API will ensure you are using the most up-to-date and secure revision. The platform will also provide security for the API and network.

Ensure the Platform Offers the Flexibility Your Client Requires

An API provider can offer a range of flexibility and scalability. Selecting a platform that offers the pricing, network, features, and scalability your client or company requires will ensure a better final product. A flexible metered or per-minute payment plan ensures you can test and implement the API without a significant investment, and your business or client can scale its services without any additional fees. 

The platform should also offer enough scalability for your client or company to add users or phone numbers as needed. A reliable network with redundancy will ensure every call is received. Your provider will also provide features such as call masking, internet fax, CNAM or caller ID management, and the option to integrate click-to-call into your software, website, or app.

Implement DID Calling With an API Provider

Implementing DID using the Numbers API from Flowroute makes providing a seamless and fast calling experience easy. Using the Numbers API, you can choose your preferred programming language and implement DID in a few lines of code. Your client or business will be able to make internal calls and conference calls from within an application in a matter of minutes. 

Callers can reach their recipient without memorizing an extension or going through a series of IVR prompts, and your business can manage its DID numbers from a simple web portal to port or purchase new numbers on demand. They’ll also receive the flexible pricing, reliability, and all the features our platform provides. Get started with a more customer-friendly experience from Flowroute.