FNB locked my account

Good day my account was locked they said because a ***** money was sent to my account and they (fnb) deducted the amount of R6,650 immediately from my account because it was part for the ***** money my account, I then contacted my client who sent me the money for a birthday decoration told him what happened and he also told me his account has also been locked and he doesn’t know the reason but he said he will call his bank which is also fnb. To cut the story short over 1 month now my account has been placed on locked I kept calling the bank(fnb) they always tell me the same thing that the investigator in charge of my case (my case number: ***) will contact me and she has never contacted me till this moment. The bank gave me her email and I sent her many email with her evidence to let her know I’m not involve into ***** I run a birthday decoration and surprise business and my business is registered, I’m also a victim here cause the money was sent to my account by a client so how can I identify a ***** money when I got a lot of client that make payments to my account for work. This particular issue has really slow down my business because right now I still have over R16k locked in my account. This is frustrating and heartbroken