Voice over IP (VoIP) does not work without an online connection, of course, but this heading refers to pure VoIP providers. In contrast to the classic combination of telephone and Internet contract, the telephone connection is decoupled from the provision of the online connection. So if you take the trouble to compare prices and provision of both services separately, you may be able to save money or get a more powerful connection. In addition, when switching Internet providers, there is no need for number porting, which is always associated with a certain risk of failure. Nothing changes on the decoupled telephone connection.
The tariffs of the offerers are throughout favorable, there are contracts without monthly basic charges (then with somewhat higher minute prices), with basic charges as well as Flatrates. These services can be used via a VoIP-capable router with any telephone, on the computer with softphone tools, and on the smartphone with apps.