FNB SMS on Insufficient fund on un-authorised debit order

I received an SMS stating I need to deposit money into my "Savings" account as a Debit order of R961 needs to be taken off. 1. There is one debit order on this account of R100 that I know off, no other debit order mandates signed. Called FNB, on the line from 8 o'clock to 8:40, spoke to 8 different people from the debit order department right through to ***** department and no one can assist. If there is an SMS send there should clearly be some record of why this was send to me. And I don't have a debit order of R961 on this account. I had to transferred all fund out of my account. Now I can't use this account as no one seems to know why I received this sms......FNB please investigate as the SMS won't just come out of nowhere. I need this account sorted out.