Welcome and thanks for posting. That's a really unusual question. I've looked at the Smart Talk help pages and found -
Using wi-fi, calls to the UK are charged at national or local rates, not international. Calls are charged as if you made the call from home, so UK time applies for call plan charging.
When using a mobile data connection such as 3G, you're likely to have to pay for roaming data charges – check with your mobile provider before you travel.
In some countries, calls made over the internet (VoIP) are not allowed. You must use BT SmartTalk in accordance with the laws of the country where you're currently located. It's your responsibility to ensure you're not using the service in places where such restrictions are in place.