EFT Payment not reflecting on my bank account.

On the 25.04.15 I received an SMS Notification from my Employer (Talent Guru) that an amount of R11796.75 was paid into my FNB Cheque account number ***. The reference no. provided was 2015-04-28/NEDBANK/***. I verified with my Employer that this amount has indeed gone off from their side and should be reflecting on my FNB account. I just had a discussion with someone from FNB contact centre who couldn't explain to me why this amount is being delayed as there was no issues whatsoever with last month's payment since this was effected via EFT and reflected on my account almost immediately. In fact FNB send me an SMS on the 12.04.15 advising me that my account was overdrawn and it was going to be closed as a result. I find this really disturbing as just a couple of days before my salary was paid into the same account, therefore why close an account without meaningful and due notice. As a financial institution that prides itself with out of this world service I find this absolutely ridiculous, and shocking for lack of a better word and seek immediate response as to why is this?