If what you mean is that there isn't the option to verify a phone number located in Nigeria is because Clickbank not accept people from Nigeria.

BUT there's a trick.

It's explained here:

http://www.nairaland.com/3714080/free-affiliate-marketing-tutorial-class

Anyway: did you consider the option to SELL your OWN PRODUCT and if you don't have these ones, buy some PLR and re-organized them?

This will give you 100% of the cost, and, if you're newbie, be realistic: you won't find so many affiliates promoting you on clickbank