Listed as slow payer by their system

I have a credit card with African bank, our arrangement was for them to deduct money on the last day of the month or Friday is month end falls under weekend, some how these guys are trying to deduct money a day before at around 10pm which bounces and eventually the following day it goes successfully , I so went to their Hatfield branch and I was told not to worry about it is how their bank operates it won't affect anything or even put me in arrears. Four weeks ago I tried applying for vehicle finance from six different dealerships and three of those dealerships rejected me because I'm messed up on Bank products apparently it's African bank and the other three dealerships says they require high deposits and balloon payment because African bank has labelled me as a slow payer.. I tried calling them without any resolution till now, debt review companies are calling me to help me with my credit which I had never skipped or underpaid