Depending on who you ask, the voice over IP (VoIP) services market is either giving ground to mobile or growing more profitable than ever. In reality, both are true. According to a recent Transparency Market Research report, the global VoIP market is projected to grow from $70.9 billion in 2013 to $136.76 billion by 2020. In general, mobile devices are winning the phone wars handily over dwindling landlines. This shift inevitably impacts VoIP as some businesses decide to go completely mobile, but the most progressive VoIP providers are actually embracing the transformation. The VoIP companies rolling out updates and new features around cloud-based access, mobility, and wireless connectivity are the ones gaining customers—as long as they don't lose the fundamentals of what makes a great VoIP service.

When choosing a VoIP service, there are 10 factors to keep in mind. The following are five features and capabilities the service should have to ensure it remains business-relevant as well as five warning signs marking a VoIP provider that may not be built to last.

Five Dos:

1. Smart Mobility
VoIP services give businesses a dedicated base of communications but that doesn't necessarily mean your employees are physically in the office. More and more VoIP providers offer real-time call forwarding from the office system to telecommuters' phone lines or designated mobile devices over 3G and 4G networks, rather than traditional Code Division Multiple Access (CDMA) or Global System for Mobile Communications (GSM) signals.

2. Bring Your Own Device (BYOD)
To enable this level of mobility, VoIP services must embrace BYOD policies to securely integrate employees' devices into the system, be it through a smartphone, tablet app or an automated business caller ID assigned to each device. The Transparency Market Research analysis shows a growing trend of BYOD increasing demand for mobile VoIP on smart devices, and projects a 16.6 percent growth in phone-to-phone VoIP subscribers by 2020.

3. Hosted VoIP
A cloud-hosted VoIP option is a great way for a business to save money over building on-premises VoIP infrastructure. Hosted VoIP solutions generally cost less upfront, with far less setup cost, so small to midsize businesses (SMBs), especially those who don't need a dedicated on-premises infrastructure, should look for a Software-as-a-Service (SaaS) offering when weighing VoIP options.

4. Wireless Collaboration
Another VoIP trend the Transparency Market Research report highlights is that providers are migrating from fixed-line voice (IP-PBX) to IP-based, wireless VoIP service. This opens a variety of new collaboration possibilities and businesses should identify the VoIP services that are taking advantage of them. Tablets and smartphones should be able to wirelessly connect into the main VoIP network and many services now offer group video calling or Web conferencing as a free add-on or built-in feature. Another feature to look out for is Web Real-Time Communication (WebRTC) integration for real-time audio and video communication from within the browser.

5. Usage Quality Remains Essential
A VoIP solution may boast the shiniest responsive interface and a wide array of mobility and wireless capabilities, but the VoIP calls still need to do the basics right: have reliable hardware, crisp call quality, and fundamental features such as integrated dial-in conferencing and speech-to-text recording transcription. Newer online VoIP services should seamlessly work with the provider's existing hardware solutions, and it's crucial to test the service across different Internet connection speeds and bandwidths to check for any degradation in audio quality, lack of dial tones, or excess echo.

Five Don'ts:

1. Overcomplicated Setup
If a business was already on the fence about investing in a VoIP service, a lengthy setup process and a clunky interface won't help. A business should receive a box or phone adapter from the service provider, hook it into a router and the enterprise or SMB landline directory, and then look at the service's (hopefully) clean and easy-to-navigate dashboard. A VoIP provider that hasn't bothered to update its user interface (UI) in a decade likely hasn't added cloud and mobile-focused functionality or other modern features either.

2. Shaky Bandwidth
As your business scales up to more employees servicing a broader customer base, VoIP bandwidth should be equipped to handle higher loads and more diverse user environments. Use a free tool to test bandwidth speed to ensure you won't be dealing with frequent outages in service availability.

3. Steep-Scale Pricing
VoIP services have traditionally charged for adding extra phone lines and installing more hardware or additional infrastructure as a business expands; cloud-hosted VoIP offerings shouldn't be trying to do the same. Interoffice calls or adding more mobile or connected devices to a monthly or annual VoIP plan shouldn't exorbitantly add to costs—especially when many VoIP services provide online calling and videoconferencing for free. SaaS VoIP services provide a significant pricing edge in terms of scaling.

4. Underwhelming Support
A VoIP service can be as technically sound as they come but ultimately your business still has to work with the people maintaining it. Gauging a VoIP service's personal touch starts with the sales staff. Watch for slow follow-ups to a product inquiry or sales calls inundating you with unwanted information rather than a researched pitch. Online reviews aren't completely reliable but take heed of multiple reports detailing troubleshooting problems around extended time on hold, inability to resolve technical problems, or communication issues with outsourced customer service staff.

5. Resistance to Change
The VoIP market is successfully adapting to the cloud and mobile-focused concerns of businesses and users, but a VoIP service is only as good as how quickly and successfully it integrates this technology. If your business has been using the same VoIP provider for a decade or more, and there are no cloud hosting, mobility, BYOD, or wireless communication and collaboration features to be found, it's time for your business to look at a VoIP service that's adapting rather than cling to a VoIP service that is stuck in the past.