VoIP solutions aimed at businesses have evolved into unified communications services that treat all communications—phone calls, faxes, voice mail, e-mail, web conferences, and more—as discrete units that can all be delivered via any means and to any handset, including cellphones. Two kinds of service providers are operating in this space: one set is focused on VoIP for medium to large enterprises, while another is targeting the small-to-medium business (SMB) market.[13]

IP communication provides for device mobility. For example, a residential broadband connection may be used as a link to a virtual private network of a corporate entity, in which case the IP address being used for customer communications may belong to the enterprise, not being the IP address of the residential ISP. Such off-premises extensions may appear as part of an upstream IP PBX. On mobile devices, e.g., a 3G handset or USB wireless broadband adapter, the IP address has no relationship with any physical location known to the telephony service provider, since a mobile user could be anywhere in a region with network coverage, even roaming via another cellular company.
Choose the service that is appropriate for your calling needs. Residential VoIP plans are cheaper than business VoIP plans because: (1) they have fewer features and (2) residential phones are used less frequently than business phones. Don’t use a residential VoIP service for a home-based business unless you’re willing to pay overage fees or to have your VoIP service canceled. VoIP providers are serious about enforcing their Fair Use guidelines.
The most widely speech coding standards in VoIP are based on the linear predictive coding (LPC) and modified discrete cosine transform (MDCT) compression methods. Popular codecs include the MDCT-based AAC-LD (used in FaceTime), the LPC/MDCT-based Opus (used in WhatsApp), the LPC-based SILK (used in Skype), μ-law and A-law versions of G.711, G.722, and an open source voice codec known as iLBC, a codec that uses only 8 kbit/s each way called G.729.
Types of Services offered Home VoIP, Business VoIP, SIP Trunking, International Calling Home VoIP, Business VoIP, International Calling Home VoIP, International Calling Plans Small Business VoIP, Residential VoIP, Reseller VoIP, Hosted PBX, Home VoIP, Business VoIP, International Calling Plans Home Phone Service, International Calling, Business Phone Service
E.164 is a global FGFnumbering standard for both the PSTN and PLMN. Most VoIP implementations support E.164 to allow calls to be routed to and from VoIP subscribers and the PSTN/PLMN.[27] VoIP implementations can also allow other identification techniques to be used. For example, Skype allows subscribers to choose "Skype names"[28] (usernames) whereas SIP implementations can use URIs[29] similar to email addresses. Often VoIP implementations employ methods of translating non-E.164 identifiers to E.164 numbers and vice versa, such as the Skype-In service provided by Skype[30] and the ENUM service in IMS and SIP.[31]
In general, the provision of VoIP telephony systems to organisational or individual users can be divided into two primary delivery methods: private or on-premises solutions, or externally hosted solutions delivered by third-party providers. On-premises delivery methods are more akin to the classic PBX deployment model for connecting an office to local PSTN networks.
Mass-market VoIP services use existing broadband Internet access, by which subscribers place and receive telephone calls in much the same manner as they would via the public switched telephone network (PSTN). Full-service VoIP phone companies provide inbound and outbound service with direct inbound dialing. Many offer unlimited domestic calling and sometimes international calls for a flat monthly subscription fee. Phone calls between subscribers of the same provider are usually free when flat-fee service is not available.[citation needed]

Because they're working across such a multitude of channels, many of today's phone systems are adopting the moniker of Unified Communications-as-a-Service (UCaaS). These are generally cloud-based, virtual PBXes (private branch exchanges) that include at least one, usually multiple, software clients to enhance their functionality on the web, desktop, and a variety of mobile devices. UCaaS systems have a wide variety of feature sets based on the tried and true VoIP. Even residential VoIP systems come with features that are simply impossible using a conventional telephone system.
Each provider will disclose international calling rates on their website and a list of features on their website. We give a standardized list for each provider (with explanations on our VoIP Calling Features page) but providers experiment with different features all the time. Check their website (using a link on their details page) to verify how each  feature works.
Such emergency services are provided by VoIP vendors in the United States by a system called Enhanced 911 (E911), based on the Wireless Communications and Public Safety Act of 1999. The VoIP E911 emergency-calling system associates a physical address with the calling party's telephone number. All VoIP providers that provide access to the public switched telephone network are required to implement E911,[34] a service for which the subscriber may be charged. "VoIP providers may not allow customers to "opt-out" of 911 service."[34]

Softphones are increasing in importance in VoIP offerings to the point that for some they're the only choice. They are a critical part of UCaaS and are as common on mobile phones and tablets as they are on desktop PCs. For workers in call centers, softphones are a common tool because of they're the front-end window of any CRM or help desk integration. So, for example, a softphone can combine a telephone conversation with text chat and screen sharing, which means a conversation between two employees can seamlessly add more participants, handle private text chats between those participants while the call is still going on, and extend to a collaboration session in which the group shares screens, documents, and data—no prep, no reserved lines, just button clicks.  

Nextiva also provides a number of helpful features for businesses working from home. For starters, there’s the Nextiva app, which lets you use your business phone number to make calls remotely from your desktop or mobile devices. Nextiva’s team collaboration tool, Cospace, also lets your team collaborate via video chat, so you can keep everyone one the same page.
You know Verizon; everybody knows Verizon. It’s a mobile leader, and its ultra-fast Fios (fiber-optic internet) service is expanding rapidly—so of course it’s also in the VoIP business. Verizon has built-in  bring-your-own-device (BYOD) solutions, as well as the internet connections (both fiber-optic and DSL) to support a reliable VoIP business service. Consolidation of all your business’s telecommunication needs into a single bill could be easily accomplished with Verizon. It would be more convenient than cheap, however.

For instance, while AT&T offers landlines with unlimited phone calls for $33.99/month, with RingCentral you can get the Essentials plan, which includes unlimited phone calls starting at just $19.99 per person per month, and you can also enjoy a more extensive list of features. On Grasshopper, the introductory plan costs as little as $26/month, but that includes 3 extensions. With residential VoIP, you have a bundle of features you couldn't find with traditional landlines. Also, because of technology's continual advancements, the features continue to improve every year without a sharp rise in costs. VoIP for home use makes sense because you derive so much more value than what the traditional phone companies of today are offering.
The Yealink Touch-sensitive HD IP Conference Phone CP920 is comprised with the Android 5.1 operating system. With a user-centric design, it combines simplicity of use with sophistication of features, being perfect for small to medium sized conference rooms. With its crystal-clear audio quality, your conversation will sound natural and bright anywhere with well-designed CP920. The Yealink CP920 can be not only paired with your mobile staff –smartphone or PC/tablet via Bluetooth, but also is a good choice for businesses that use a public switched telephone network (PSTN) after combining with CPN10 PSTN Box. As a valuable complement for your conference room, CP920 conference phone strikes an excellent balance between ease-of-use and powerful features, giving you a simply and clearly engaging business conference experience.
While the exact features offered in any particular UCaaS solution can change radically from vendor to vendor, most include options for video conferencing, shared meeting and document collaboration tools, integrated faxing, mobile VoIP integration, and device-independent softphone clients. All of these options let customers look at communications in a whole new way, namely, in an a menu-style manner where they can implement only those features their business needs and then access them any time they want and in any combination. This new approach to business communications has been growing steadily among customers over the past few years as recent research from Statista bears out.  
Not every internet connection is VoIP ready, so before you sign up, make sure that your line will provide you with the level of VoIP speed and service you need. You can easily find resources online for checking the speed and call quality of your connection. The quality of your connection can potentially impact the clarity of your calls, so pay close attention. 
Vonage Business is the biggest name in VoIP, and the good news is it’s a leader in residential VoIP too. Vonage has powerful, nationwide infrastructure, ensuring 100% uptime whenever you make or receive a VoIP call through your home IP phone or the Vonage smartphone app. All pricing packages are billed monthly, with no contracts. However, if you agree to be billed annually, Vonage will reward you with close to a 50% discount on your first 6 months.
A key attraction of VoIP is that it gives these systems the flexibility to work in a wide variety of environments ranging from analog desk phones to softphones piggy-backing on a cell phone. These systems can often also integrate all or part of their softphone clients into other back-office applications, like your customer relationship management (CRM) or help desk platforms. Simply picture the standard interface of such an app that suddenly sports a dial pad and some function buttons as a pop-up screen and you'll have a very basic idea of how some of this works. In addition, these cloud based systems can have a variety of phone numbers in global locations, so that your customers can have free access to your phone at little or no charge.