Why are my cards not working for Apple billing? I'm in Nigeria

I suggest you ask Apple. This appears to be a fairly common issue from people saying they are in Nigeria, but I do not see anything explaining it.

Refer to this page for Apple Support features ➔ Contact - Official Apple Support

Select from the presented options until you find a solution for your issue, or see if there is a chat or phone call contact method offered lower on the page (you sometimes have to narrow down the options multiple times before this is shown). If you do not see your issue, keep experimenting with any series of selections until you reach one that offers a chat session or a telephone call and get the representative to redirect you.

This page has telephone numbers for contacting Apple for support and service ➔ Contact Apple for support and service - Apple Support