FUNDS DISAPPEAR WITH NO TRACE IN FNB ACCOUNT

I received payment into my FNB account amounting to R75 000 (3*25000) on 3 February 2020 and they appeared in my account and I transacted. When I tried transacting on the 5th of February my account was blocked but there was an available balance of R 16000. I then received a call yesterday informing me that my account was overdrawn with R60 000 and I had 24 hours to pay the money even though I did not have an overdraft account. I had to go through my account and luckily managed to realize that there were 3 transactions that have disappeared totally from my account with no history that they were ever there. One wonders what was going to happen if I failed to pick up the actual transactions Involved? I was going to lose R75 000 just like that.

I contacted FNB and informed them of the situation last night and I was promised that I will get a call first thing in the morning to address the situation. Its now 3:30 and I haven't been contacted, my suspicion is that they expect me to call again to help them fix their mess this after I have contacted them via app chat highlighting the situation. FNB was quick to give me 24 hours to pay the money yet they cannot call me to resolve their mess in the same time.

I questioned the legality of funds disappearing without a trace, if this can happen whats to say small amounts are disappearing without being noticed in hundreds of accounts? Were is the integrity of the records and security of our funds? How can a transaction that got recorded in my account just disappear without a trace?