I am developing a mobile app and will sell points within the app. My app's users need to be able to purchase points with their phone credit, something like what 2go did; allowing users purchase 2gp credits with their phone balance.

I need an API that is affordable to deploy and use (initial setup costs and purchase charges) because I intend to sell points cheaply(from #100). The few I have found online are costly to setup (from #150k) and costly to run (one charges as high as (#100 per transaction).

I know that a cheap alternative exists because 2go credits start from #30.

The API can either be SMS or USSD. I need suggestions from people who know or have implemented similar systems in past projects, thanks.

cc: segmond, DanieltheGeek, dhtml18...