I want my money FNB

I recently opened a business account on FNB and used their speed point machine to run my business(I sell clothes, sneakers, weaves and iPhones etc) so a customer bought items of an amount of R38 500 swiping with the machine and the transaction was successful,but FNB froze the funds and they said my identity was listed on the South African *****ulent activity (due to matric certificate duplicate) now my question is how can they take my money because of that,any who can help me please I'm suffering here with stress.