An important disadvantage of the landline is that you cannot easily scale it up or down. This is why many companies with rapidly expanding or contracting business sizes prefer VoIP because it allows enterprise management to easily add, edit or even delete user rights centrally through the control panel. It is not necessary to follow the tedious processes involved if you are using a regular landline. This makes internet phone technology significantly more suitable for large business organizations.
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.  
A high speed Internet connection is required to "carry" your calls so if you have an Internet outage (or your ISP has an outage) then your phone service will not work. Internet services have improved significantly in the last few years and outages tend to be much less common than they use to be. Again, if you have a cell phone then this may not be an issue for you.
It's also critical that you consider the impact of mergers and acquisitions on your phone system, both from your own organization's perspective as well as your VoIP provider. Because VoIP systems turn calls into data, the whole process isn't as plug-and-play standards-based as the old-fashioned analog phone system might have been. Should your company merge with or purchase another, VoIP compatibility will become another significant IT issue.
What makes SIP so popular is not only that it's deep and flexible, but also because it was purpose-built to engage in multimedia (meaning not just audio but also video and even text) communications over TCP/IP networks. For VoIP calls, SIP can set up calls using a number of IP-related protocols, including the Stream Control Transmission Protocol (SCTP), the Transmission Control Protocol (TCP), and the User Datagram Protocol (UDP), among others. But it can also handle other functions, including session setup (initiating a call at the target endpoint—the phone you're calling), presence management (giving an indicator of whether a user is "available," "away," etc.), location management (target registration), call monitoring, and more. Despite all that capability, SIP is simple compared to other VoIP protocols primarily because it's text-based and built on a simple request/response model that's similar in many ways to both HTTP and SMTP. Yet, it's still capable of handling the most complex operations of business-grade PBXes.  
The advanced Yealink EXP20 is an ideal IP phone system for receptionists, administrative assistants or contact center workers who need to monitor and manage a large volume of calls on a regular basis. The Yealink EXP20 is flexible, powerful and contains a large user-friendly liquid crystal display (LCD) interface that measures 160×320 pixels. As well as contains 20 physical, dual-color LED keys. The additional screen space and added number of buttons simplifies user navigation and streamlines essential operational. Up to six EXP20 phone systems can be strung together on a single daisy chain.
Step 3 is all about reviews. However, as this section is about comparison we are introducing our Ratings Comparison Tool in this section. This tool allows the ability to select from a list of service providers and compare user review ratings side by side. You can also select specific rating categories for a seletion of providers and visually compare in a graphical representation.

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.

There are some solutions to this issue if you have concerns. The most obvious is to utilize Uninterruptable Power Supplies (UPS) for those short outages, or a generator if you live somewhere where outages are more common (and for your fridge!). With so many people having cell phones these days most people will not be too concerned with this issue, especially when they consider the money they are saving. Most services include a call forwarding feature so you can always set that up to go to your cell phone so you do not miss important calls.