How to make a call?

VoIP phone adapter connects a simple landline to the Internet network.
IP phone connects directly to the netowork.

These solutions work independently of the computer.

Download a softphone and install it on your computer. You can talk by using headphones with microphone.

This solution works only with your computer turned on.

Mobile phones with WiFi function enable you to connect to the wireless network.

This solution works only in places with an access to the wireless network.

How to dial a number?

[without zero] city prefix code + telephone number
e.g. 22xxxxxxx (Warsaw)
mobile phones:
[without zero] mobile phone number
e.g. 608xxxxxx

Internationals calls:
00 + country prefix code + city prefix code + telephone number
e.g. 004420xxxxxxxx (London)
mobile phones:
00 + country prefix code + (foreign) mobile phone number
e.g. 0044xxxxxxxxxx (English mobile phone)