Pay to cell situation

I am saddaned about an experience I had with FNB today. Someone sent me money for a painful family situation. I am unemployed since 2019 due to a retrenchment and still trying to find my feet. I have an account with FNB that had an overdraft which I negotiated with debt collectors that I will pay as and when money comes in. Today when someone sent me money through pay to cell FNB top all that money to the overdraft. What makes me sad is that how did the system choose the account in negative when I have other accounts open that are active. There was not even a chance to negotiate the situation. Sadly I have a funeral and Covid related medicines to get. I will really be glad if someone may grant me amnesty and reverse the money as I need it. I also have other proposals on how I can sign an acknowledgement of debt for deductions to be made from my small business account to replace the 2000 aslong as I can be reimbursed for now to meet my funeral and sad Covid medication situation.