Undesirable service

I asked FNB to put a cap on my overdraft of R2000 as I found out after years of having huge negative balances that they continue honouring transactions despite my overdraft being done. I even took them to the banking ombudsman and they assured me that a cap has been put on my overdraft but as I speak my account has exceeded the overdraft limit by over R800,why? My ID number is ***.