Terms & conditions.
> Free Skype Calls on 3
Free Skype calls on 3 are for Skype-to-Skype calls made from the UK and are available on most 3 mobiles. Pay As You Go customers can make free Skype-to-Skype calls and instant messages (IM), as long as they have credit.
Access to Skype on 3 is subject to you inserting your 3 SIM into a compatible 3 mobile. You may be required to download the Skype application from 3 Services in Planet 3.
Call Phones Abroad on Skype
Unlimited international calls from Skype are for calls from Skype to standard international landlines in selected countries (excluding the country you’re calling from). This is subject to buying Skype credit or a Skype calling subscription direct from Skype at Skype.com