Double debited

I have a problem with FNB, a serious one. FNB double debited my account on the 31st. I called immediately (Monday) and I was assured the money will be in my account latest today. I woke up to a bank account that had no money in sight. I called in this morning, a lady that was assisting me said the supervisor will call me and they will reverse the funds as she has done an urgent reversal request. I am still waiting... Nedbank made the same error and my account was credited in 10 minutes after I made a complain on Twitter where I also tagged FNB who has decided to ignore me.

Kindly assist because I am now stuck.