Why hasnt the united nations questioned china for not extending nigeria visa?

Question

I believe every business visa is ment to be extended if the time given to the immigrant is not enough to rap up the business deal but the chinese government has refused to extend any visa that is contained in nigerian passport but they extend any other african country except nigeria....since our government(nigerian government)has refused to forward that question to the chinese government,so i decided to bring it up for a better answer.

Answer 1

Extension of a visa is valid if there is an authorized reason.

Answer 2

Visa reciprocity is a matter between individual nations, and is not under the purview of the United Nations.