FNB Took money without authorisation

I am an FNB Platinum client and have been banking with them for nearly 10 years. Unfortunately I find myself unemployed since March this year and have no income. This morning I get an SMS telling me that discovery has refunded my medical savings account. A few hours later I get another SMS from FNB telling me that they have taken R450 from my account towards a loan account. Unaware of any loan accounts I have with them I decided to give the premier suite a call. I spoke to a helpful consultant named Charlotte who went through my account and said she will get the relevant department to call me. A little while later I get a call from somebody named Prudence from FNB's CBS legal services. She was absolutely rude and robotic and had no telephone etiquette whatsoever. She tells me that they tried calling me and got no answer so they just took the money and there is nothing I can do about it. And she has the audacity to end the sentence with OK? Of course it is NOT OK. And when I told her they should have called me to make an arrangement she says well they tried to call and got no answer so they are not going to refund me. That is pathetic from FNB