Stage 1 - setting the scene
The first step in adopting VOIP is deciding what you want out of it. Do you want to keep 'sweating' your existing analogue PBX, coupling it with VOIP to save on call costs, or do you want it as your sole voice solution, for extra savings and functions such as unified communications?
If the former, the provider will simply put in a gateway device on your premises, which will receive your analogue phone lines on one end and turn them into VOIP channels going out on your Internet line, for an instant 30% saving on call costs. A small gateway turning a few high-intensity phone lines into IP channels can be cost-effective (the gateway will attract an upfront cost).
If you need to do an upgrade or replace your PBX, or you're adding branches, a move to VOIP makes perfect sense. Better yet, go for full cloud VOIP (where the PBX is hosted by your VOIP provider, meaning you can say goodbye to PBX cost and operations headaches, but still pay for handsets and a gateway if the old PBX is kept as backup). Either way, the VOIP provider can then move onto the next question.
Since VOIP falls under the IT umbrella, your VOIP provider should from here on in be talking to your IT manager or support company, to ensure trouble-free installation, running and support of your system as well as beneficial costing. Their conversation will probably take a simple Q&A format, as follows:
Training on the phone system's features allows smooth adoption. VOIP systems should come with a manual.
The truth about VOIP systems is that they're not different, in the main, from telephony as you know it. You will continue to take and make calls in exactly the same way, and adoption need not scare you. In addition, you will benefit from enormously beneficial extra features that improve workflow and communication.