International calls don't have to be expensive
Although most landline telephony contracts these days feature a flat rate, in many cases the flat rate covers only calls made within the network. Calls to other providers' telephone networks and non-European international calls are a different story. Such cases lend themselves to Internet telephony, also known as Voice over IP (VoIP). Here the voice data are transmitted to your calling partner via the existing Internet connection.
Economical calling over VoIP
As a FRITZ!Box user you already have the ideal VoIP telephone system at your disposal: The user interface provides for simple configuration of up to 20 Internet telephone numbers. This means a different number can be configured for every outside network or country. Make sure that the VoIP providers support SIP (Session Initiation Protocol). See the provider comparisons available on the Web.
Using dialing rules you can specify which provider should be used for which target numbers. The most economical rates are listed online. For instructions on how to configure your FRITZ!Box for Internet telephony, read the example for the FRITZ!Box 7390.
Call Australia for free
Maybe your daughter is planning to spend a year as an au pair in Australia. Then she could take advantage of the possibility to connect her smartphone with your home network via VPN. Over WiFi, perhaps at her host family's home, she can connect to your FRITZ!Box using a free VPN connection. Then she can call her family and friends at the rates configured in the FRITZ!Box at home. No international charges are incurred for the call from Australia to her home country, and the smartphone's data usage remains untouched.