They don't want to close the vehicle finance

they told me to put a 90 days notice in order for me to settle my vehicle finance, i did that. they gave me a settlement letter with the amount to pay(which i had to fight to get it). the total amount was paid to standard bank a day after the date stipulated on the letter. i even paid R100 extra. so now the account is R100 credit to me. which means standard bank owe me. NOW, with confidence, i asked standard bank to close my account as i dont owe anything to them but they owe me. NO, ACCOUNT CANNOT BE CLOSED BECAUSE I PAID THE SETTLEMENT MONEY A DAY AFTER THE LETTER... Really now?????? does it matter or the main thing is whether i owe you or not??? can you please close this account before month end because i know you gonna deduct the monthly installment if this acc is not close and for me to get my refund with take 10 years. I need the original NATIS documents as well. is there anything that standard bank can do without their client complaining??? i cant wait to change this bank joooh...