You want to get on the cheapest flight from Abuja (Nigeria) to Johannesburg (South Africa).
The way to make sure that you get on the cheapest flight is to:
type your flight details into the search engine on the left and see what airfare it spits out
check the airfare of every airline flying your route
News
2012. Air Nigeria stops operating, meaning no more 1-stop flights with its from Abuja to JNB (via Lagos).
2009. Bellview Airlines ceases operations, and along with that event its 1-stop flights from Abuja to Joburg via Lagos also cease.