The main reason for a business to change to VoIP technology is to save costs.
Naturally, calls using the internet are generally perceived to be free of charge. However, this is not always the case as calls at some point have to be transported across a Public Services Telephone Network (PSTN).
In many instances savings can be made against phones and landlines, especially if an organisation is making many international calls or has multiple offices, where savings can be made from making internal calls from one office to another using VoIP rather than landlines.