Statement balance is not settlement balance

I went online to African bank last week to retrieve a settlement amount for my credit card account, no one got back to me. i then looked at the online balance and i paid the balance. i then called someone at African bank told them that i paid the balance as per the statement to close the account. i was then told that i would need to call back in 24 hours to close the account as the money does not yet reflect. why was i not then told that the amount i paid was incorrect as i specified and i was not even offered to have a check run as to a settlement amount. now i have to pay an extra R300.