We've been working on upgrading our payment system so that it's integrated with the ClearSMS application.  This means that you don't have to go through the external cart to buy credits. 

We'll it took 3 times the amount of time we had expected (banks are ruthless), but we're finished.  This reminds me of a post I had read a while back from a Web start-up, that they had spent more time writing the payment system than the actual product.  I said to myself - no way! I don't believe it...