The website claims the cheapest int'l call rates from your mobile, examples being Australia and New Zealand 6p per minute, South Africa 8p Per Min, USA from 5p Per Minute. The full llist can be found on-line at the website. UK Calls are 15p per minute to any network I believe.
You'll also recieve an extra £25 on your 1st top up.
I believe these are a virtual Network of T-Mobile.
£25 should read 25%