My bank account was closed without any notice

Capitec bank closed my account without notifying me, when I went to ask whats wrong I was told Standard bank told them to close it because their account sent ***** money to another account which ended up in my account. I asked to speak to someone in charge of the case they denied, I asked more details about the money thry denied telling me until I threatened them by saying I will report to bank Obudsman then they told me the amount of R4500 came in on the 17th of March and promised to release my other funds if I produce proof of where it came from, its been 7days since my account was closed but Im not getting any feedback. I went back to my notification smses and saw that the money came from my brothers account, he then went to check with the bank and found that his account is also closed without any notice but its closed for the amount that came in on the 2nd of April still they cant prove to him that its *****. They are quiet yet they dont want to give me contact numbers for people responsible for the case. Ive never dealt with so much incompetence I went to the bank twice already but I come out with nothing but empty promises. I also went to Standard bank who said cant help.