I've got the same deal, different phone though. I've had no unexpected costs or funny problems so far. I get my credit every month, and any unused credit is rolled over from the last month.
I thought the deal was too good to be true, but I did it and switched from Vodacom. I like the fact that the money you pay is the exactly the credit you get out for making calls. None of this pay a monthly contract fee and get a 'free' minute BS.
As far as catches go, check you understand the terms and conditions for the call rates and unlimited sms. E.g. international SMS not included. I was confused about their call rates but i called them and they helped me out
I thought the deal was too good to be true, but I did it and switched from Vodacom. I like the fact that the money you pay is the exactly the credit you get out for making calls. None of this pay a monthly contract fee and get a 'free' minute BS.
As far as catches go, check you understand the terms and conditions for the call rates and unlimited sms. E.g. international SMS not included. I was confused about their call rates but i called them and they helped me out