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:
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