I want to sue african bank

I have paid up my loan with african bank in December but they are still debiting my bank account, they did it twice on two consecutive days I mean that must be *******!!!. When they did it the first time I called them and they said they will request for the account to be closed and even sent me an sms them boom again today they debit me again. I can not perform a reversal on my account but I need to use my money and they have wiped out my account, I don't know what to do anymore. It's 5 am in the morning and I need to get money to my child to go see a doctor but it doesn't seem like she will since African bank decided to take money that wasn't owed to them unfairly. I wish I knew the process of suing them for causing so much inconvenience to me