It is very convenient to have an internet telephone account as an expat, because calling a land line is around 1-2 eurocent/minute and one can have a dedicated phone number, that one can bring easily to a new country. I prefer to use standardised solutions (such as SIP), because there are more software and specialised hardwares available and I am not locked to one company. Two providers those I use:
Neophone – Pro: European and USA landlines around – 1,7-2 eurocents/minute, Mobiles 12-17 eurocents/minute, pay per second Con: basic user interface, can be charged only with Hungarian credit card
Sipgate – Pro: German phone number with proper area code (e.g. having a prefix from Berlin, but it rings in Hungary), user friendly and professional interface Con: pay per minute, calling Hungary costs twice as much than Neophone.
User agents (softwares) to call:
Media5-fone (iOS, Android) – Pro: very powerful and very stable Con: have to pay to remove the ads, the user interface seems a bit clumsy.
Telephone (Mac) – Pro: free and open source app with an user-friendly interface