The whole nature of a IP phone system is its flexibility, providing you instant access to your phone system anywhere in the world with a broadband connection, be it by cable, WiFi or 3G. Ultimately, you could have a unified, single platform phone system across as many offices as required, bringing all of the administration, support and costs under one roof, all via a highly secure and reliable service.
There are several advantages to using a voice over IP system. The biggest single advantage VoIP has over standard telephone systems is cost.
In addition, international calls using VoIP are usually very inexpensive and national 01 and 02 prefix calls are free of charge meaning you can put an end to those expensive unpredictable monthly phone bills.