I am always on the lookout for security issues in developing countries. The unique nature of payment systems in sub saharan countries create a new problem set of security issues. See this post article about how some university students were able to purchase mobile phone cards.
The payment model used by the bank is very simple.
1. Clients purchase rechargeable units.
2. The clients account is debited
3. The service providers account is then credited.
There is absolutely porous security in this model. These scammers just took advantage of the time period between the credit and the debit to dupe the banks. There are no futher details about the exact attack but is it not scary that this fraud was not discovered earlier.