If you only want to use VOIP to communicate with other users in your VoIP network, you can do that free of charge. If however you want to be able to use VoIP to make and receive CALLS to/from people who are out of your VoIP network or do not have VoIP, you will need to subscribe to a VoIP service provider plan, and a gateway service may be also NEEDED that PROVIDES a bridge between VoIP and the conventional phone networks.

If you only want to use VoIP to communicate with other users in your VoIP network, you can do that free of charge. If however you want to be able to use VoIP to make and receive calls to/from people who are out of your VoIP network or do not have VoIP, you will need to subscribe to a VoIP service provider plan, and a gateway service may be also needed that provides a bridge between VoIP and the conventional phone networks.