Who is Charles Ibe from No Longer at Ease and what is their importance?

Charles Ib is a messenger in Obi Okonkwo's building, Ibe has been avoiding him since the time limit for repaying a thirty-shilling loan passes. Obi finds the promissory note when his £42 insurance bill arrives and he has but £13 in the bank. He tells Ibe, who needs the money when his wife gives birth to a fifth child, that debts never rot and threatens to report him to Green if he fails to pay up by the end of December.